Subject: [RFC v4 PATCH 0/5] NOT FOR MERGE - ro protection for dynamic data
This patchset introduces the possibility of protecting memory that has
been allocated dynamically.
The memory is managed in pools: when a pool is made R/O, all the memory
that is part of it, will become R/O.
A R/O pool can be destroyed to recover its memory, but it cannot be
turned back into R/W mode.
This is intentional and this feature is meant for data that doesn't need
further modifications, after initialization.
An example is provided, showing how to turn into a boot-time option the
writable state of the security hooks.
Prior to this patch, it was a compile-time option.
This is made possible, thanks to Tetsuo Handa's rewor of the hooks
structure (included in the patchset).
Notes:
* I have performed some preliminary test on qemu x86_64 and the changes
seem to hold, but more extensive testing is required.
* I'll be AFK for about a week, so I preferred to share this version, even
if not thoroughly tested, in the hope to get preliminary comments, but
it is rough around the edges.
Igor Stoppa (4):
Protectable Memory Allocator
Protectable Memory Allocator - Debug interface
Make LSM Writable Hooks a command line option
NOT FOR MERGE - Protectable Memory Allocator test
Tetsuo Handa (1):
LSM: Convert security_hook_heads into explicit array of struct
list_head
include/linux/lsm_hooks.h | 412 ++++++++++++++++++++---------------------
include/linux/page-flags.h | 2 +
include/linux/pmalloc.h | 20 ++
include/trace/events/mmflags.h | 1 +
init/main.c | 2 +
mm/Kconfig | 11 ++
mm/Makefile | 4 +-
mm/pmalloc.c | 340 ++++++++++++++++++++++++++++++++++
mm/pmalloc_test.c | 172 +++++++++++++++++
mm/usercopy.c | 24 ++-
security/security.c | 58 ++++--
11 files changed, 814 insertions(+), 232 deletions(-)
create mode 100644 include/linux/pmalloc.h
create mode 100644 mm/pmalloc.c
create mode 100644 mm/pmalloc_test.c
--
2.9.3
From: Tetsuo Handa <[email protected]>
Commit 3dfc9b02864b19f4 ("LSM: Initialize security_hook_heads upon
registration.") treats "struct security_hook_heads" as an implicit array
of "struct list_head" so that we can eliminate code for static
initialization. Although we haven't encountered compilers which do not
treat sizeof(security_hook_heads) != sizeof(struct list_head) *
(sizeof(security_hook_heads) / sizeof(struct list_head)), Casey does not
like the assumption that a structure of N elements can be assumed to be
the same as an array of N elements.
Now that Kees found that randstruct complains about such casting
security/security.c: In function 'security_init':
security/security.c:59:20: note: found mismatched op0 struct pointer types: 'struct list_head' and 'struct security_hook_heads'
struct list_head *list = (struct list_head *) &security_hook_heads;
and Christoph thinks that we should fix it rather than make randstruct
whitelist it, this patch fixes it.
It would be possible to revert commit 3dfc9b02864b19f4, but this patch
converts security_hook_heads into an explicit array of struct list_head
by introducing an enum, due to reasons explained below.
Igor proposed a sealable memory allocator, and the LSM hooks
("struct security_hook_heads security_hook_heads" and
"struct security_hook_list ...[]") will benefit from that allocator via
protection using set_memory_ro()/set_memory_rw(), and that allocator
will remove CONFIG_SECURITY_WRITABLE_HOOKS config option. Thus, we will
likely be moving to that direction.
This means that these structures will be allocated at run time using
that allocator, and therefore the address of these structures will be
determined at run time rather than compile time.
But currently, LSM_HOOK_INIT() macro depends on the address of
security_hook_heads being known at compile time. If we use an enum
so that LSM_HOOK_INIT() macro does not need to know absolute address of
security_hook_heads, it will help us to use that allocator for LSM hooks.
As a result of introducing an enum, security_hook_heads becomes a local
variable. In order to pass 80 columns check by scripts/checkpatch.pl ,
rename security_hook_heads to hook_heads.
Signed-off-by: Tetsuo Handa <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Paul Moore <[email protected]>
Cc: Stephen Smalley <[email protected]>
Cc: Casey Schaufler <[email protected]>
Cc: James Morris <[email protected]>
Cc: Igor Stoppa <[email protected]>
Cc: Christoph Hellwig <[email protected]>
---
include/linux/lsm_hooks.h | 412 +++++++++++++++++++++++-----------------------
security/security.c | 31 ++--
2 files changed, 223 insertions(+), 220 deletions(-)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 080f34e..ac22be3 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1663,219 +1663,220 @@ union security_list_options {
#endif /* CONFIG_AUDIT */
};
-struct security_hook_heads {
- struct list_head binder_set_context_mgr;
- struct list_head binder_transaction;
- struct list_head binder_transfer_binder;
- struct list_head binder_transfer_file;
- struct list_head ptrace_access_check;
- struct list_head ptrace_traceme;
- struct list_head capget;
- struct list_head capset;
- struct list_head capable;
- struct list_head quotactl;
- struct list_head quota_on;
- struct list_head syslog;
- struct list_head settime;
- struct list_head vm_enough_memory;
- struct list_head bprm_set_creds;
- struct list_head bprm_check_security;
- struct list_head bprm_secureexec;
- struct list_head bprm_committing_creds;
- struct list_head bprm_committed_creds;
- struct list_head sb_alloc_security;
- struct list_head sb_free_security;
- struct list_head sb_copy_data;
- struct list_head sb_remount;
- struct list_head sb_kern_mount;
- struct list_head sb_show_options;
- struct list_head sb_statfs;
- struct list_head sb_mount;
- struct list_head sb_umount;
- struct list_head sb_pivotroot;
- struct list_head sb_set_mnt_opts;
- struct list_head sb_clone_mnt_opts;
- struct list_head sb_parse_opts_str;
- struct list_head dentry_init_security;
- struct list_head dentry_create_files_as;
+enum security_hook_index {
+ LSM_binder_set_context_mgr,
+ LSM_binder_transaction,
+ LSM_binder_transfer_binder,
+ LSM_binder_transfer_file,
+ LSM_ptrace_access_check,
+ LSM_ptrace_traceme,
+ LSM_capget,
+ LSM_capset,
+ LSM_capable,
+ LSM_quotactl,
+ LSM_quota_on,
+ LSM_syslog,
+ LSM_settime,
+ LSM_vm_enough_memory,
+ LSM_bprm_set_creds,
+ LSM_bprm_check_security,
+ LSM_bprm_secureexec,
+ LSM_bprm_committing_creds,
+ LSM_bprm_committed_creds,
+ LSM_sb_alloc_security,
+ LSM_sb_free_security,
+ LSM_sb_copy_data,
+ LSM_sb_remount,
+ LSM_sb_kern_mount,
+ LSM_sb_show_options,
+ LSM_sb_statfs,
+ LSM_sb_mount,
+ LSM_sb_umount,
+ LSM_sb_pivotroot,
+ LSM_sb_set_mnt_opts,
+ LSM_sb_clone_mnt_opts,
+ LSM_sb_parse_opts_str,
+ LSM_dentry_init_security,
+ LSM_dentry_create_files_as,
#ifdef CONFIG_SECURITY_PATH
- struct list_head path_unlink;
- struct list_head path_mkdir;
- struct list_head path_rmdir;
- struct list_head path_mknod;
- struct list_head path_truncate;
- struct list_head path_symlink;
- struct list_head path_link;
- struct list_head path_rename;
- struct list_head path_chmod;
- struct list_head path_chown;
- struct list_head path_chroot;
+ LSM_path_unlink,
+ LSM_path_mkdir,
+ LSM_path_rmdir,
+ LSM_path_mknod,
+ LSM_path_truncate,
+ LSM_path_symlink,
+ LSM_path_link,
+ LSM_path_rename,
+ LSM_path_chmod,
+ LSM_path_chown,
+ LSM_path_chroot,
#endif
- struct list_head inode_alloc_security;
- struct list_head inode_free_security;
- struct list_head inode_init_security;
- struct list_head inode_create;
- struct list_head inode_link;
- struct list_head inode_unlink;
- struct list_head inode_symlink;
- struct list_head inode_mkdir;
- struct list_head inode_rmdir;
- struct list_head inode_mknod;
- struct list_head inode_rename;
- struct list_head inode_readlink;
- struct list_head inode_follow_link;
- struct list_head inode_permission;
- struct list_head inode_setattr;
- struct list_head inode_getattr;
- struct list_head inode_setxattr;
- struct list_head inode_post_setxattr;
- struct list_head inode_getxattr;
- struct list_head inode_listxattr;
- struct list_head inode_removexattr;
- struct list_head inode_need_killpriv;
- struct list_head inode_killpriv;
- struct list_head inode_getsecurity;
- struct list_head inode_setsecurity;
- struct list_head inode_listsecurity;
- struct list_head inode_getsecid;
- struct list_head inode_copy_up;
- struct list_head inode_copy_up_xattr;
- struct list_head file_permission;
- struct list_head file_alloc_security;
- struct list_head file_free_security;
- struct list_head file_ioctl;
- struct list_head mmap_addr;
- struct list_head mmap_file;
- struct list_head file_mprotect;
- struct list_head file_lock;
- struct list_head file_fcntl;
- struct list_head file_set_fowner;
- struct list_head file_send_sigiotask;
- struct list_head file_receive;
- struct list_head file_open;
- struct list_head task_create;
- struct list_head task_alloc;
- struct list_head task_free;
- struct list_head cred_alloc_blank;
- struct list_head cred_free;
- struct list_head cred_prepare;
- struct list_head cred_transfer;
- struct list_head kernel_act_as;
- struct list_head kernel_create_files_as;
- struct list_head kernel_read_file;
- struct list_head kernel_post_read_file;
- struct list_head kernel_module_request;
- struct list_head task_fix_setuid;
- struct list_head task_setpgid;
- struct list_head task_getpgid;
- struct list_head task_getsid;
- struct list_head task_getsecid;
- struct list_head task_setnice;
- struct list_head task_setioprio;
- struct list_head task_getioprio;
- struct list_head task_prlimit;
- struct list_head task_setrlimit;
- struct list_head task_setscheduler;
- struct list_head task_getscheduler;
- struct list_head task_movememory;
- struct list_head task_kill;
- struct list_head task_prctl;
- struct list_head task_to_inode;
- struct list_head ipc_permission;
- struct list_head ipc_getsecid;
- struct list_head msg_msg_alloc_security;
- struct list_head msg_msg_free_security;
- struct list_head msg_queue_alloc_security;
- struct list_head msg_queue_free_security;
- struct list_head msg_queue_associate;
- struct list_head msg_queue_msgctl;
- struct list_head msg_queue_msgsnd;
- struct list_head msg_queue_msgrcv;
- struct list_head shm_alloc_security;
- struct list_head shm_free_security;
- struct list_head shm_associate;
- struct list_head shm_shmctl;
- struct list_head shm_shmat;
- struct list_head sem_alloc_security;
- struct list_head sem_free_security;
- struct list_head sem_associate;
- struct list_head sem_semctl;
- struct list_head sem_semop;
- struct list_head netlink_send;
- struct list_head d_instantiate;
- struct list_head getprocattr;
- struct list_head setprocattr;
- struct list_head ismaclabel;
- struct list_head secid_to_secctx;
- struct list_head secctx_to_secid;
- struct list_head release_secctx;
- struct list_head inode_invalidate_secctx;
- struct list_head inode_notifysecctx;
- struct list_head inode_setsecctx;
- struct list_head inode_getsecctx;
+ LSM_inode_alloc_security,
+ LSM_inode_free_security,
+ LSM_inode_init_security,
+ LSM_inode_create,
+ LSM_inode_link,
+ LSM_inode_unlink,
+ LSM_inode_symlink,
+ LSM_inode_mkdir,
+ LSM_inode_rmdir,
+ LSM_inode_mknod,
+ LSM_inode_rename,
+ LSM_inode_readlink,
+ LSM_inode_follow_link,
+ LSM_inode_permission,
+ LSM_inode_setattr,
+ LSM_inode_getattr,
+ LSM_inode_setxattr,
+ LSM_inode_post_setxattr,
+ LSM_inode_getxattr,
+ LSM_inode_listxattr,
+ LSM_inode_removexattr,
+ LSM_inode_need_killpriv,
+ LSM_inode_killpriv,
+ LSM_inode_getsecurity,
+ LSM_inode_setsecurity,
+ LSM_inode_listsecurity,
+ LSM_inode_getsecid,
+ LSM_inode_copy_up,
+ LSM_inode_copy_up_xattr,
+ LSM_file_permission,
+ LSM_file_alloc_security,
+ LSM_file_free_security,
+ LSM_file_ioctl,
+ LSM_mmap_addr,
+ LSM_mmap_file,
+ LSM_file_mprotect,
+ LSM_file_lock,
+ LSM_file_fcntl,
+ LSM_file_set_fowner,
+ LSM_file_send_sigiotask,
+ LSM_file_receive,
+ LSM_file_open,
+ LSM_task_create,
+ LSM_task_alloc,
+ LSM_task_free,
+ LSM_cred_alloc_blank,
+ LSM_cred_free,
+ LSM_cred_prepare,
+ LSM_cred_transfer,
+ LSM_kernel_act_as,
+ LSM_kernel_create_files_as,
+ LSM_kernel_read_file,
+ LSM_kernel_post_read_file,
+ LSM_kernel_module_request,
+ LSM_task_fix_setuid,
+ LSM_task_setpgid,
+ LSM_task_getpgid,
+ LSM_task_getsid,
+ LSM_task_getsecid,
+ LSM_task_setnice,
+ LSM_task_setioprio,
+ LSM_task_getioprio,
+ LSM_task_prlimit,
+ LSM_task_setrlimit,
+ LSM_task_setscheduler,
+ LSM_task_getscheduler,
+ LSM_task_movememory,
+ LSM_task_kill,
+ LSM_task_prctl,
+ LSM_task_to_inode,
+ LSM_ipc_permission,
+ LSM_ipc_getsecid,
+ LSM_msg_msg_alloc_security,
+ LSM_msg_msg_free_security,
+ LSM_msg_queue_alloc_security,
+ LSM_msg_queue_free_security,
+ LSM_msg_queue_associate,
+ LSM_msg_queue_msgctl,
+ LSM_msg_queue_msgsnd,
+ LSM_msg_queue_msgrcv,
+ LSM_shm_alloc_security,
+ LSM_shm_free_security,
+ LSM_shm_associate,
+ LSM_shm_shmctl,
+ LSM_shm_shmat,
+ LSM_sem_alloc_security,
+ LSM_sem_free_security,
+ LSM_sem_associate,
+ LSM_sem_semctl,
+ LSM_sem_semop,
+ LSM_netlink_send,
+ LSM_d_instantiate,
+ LSM_getprocattr,
+ LSM_setprocattr,
+ LSM_ismaclabel,
+ LSM_secid_to_secctx,
+ LSM_secctx_to_secid,
+ LSM_release_secctx,
+ LSM_inode_invalidate_secctx,
+ LSM_inode_notifysecctx,
+ LSM_inode_setsecctx,
+ LSM_inode_getsecctx,
#ifdef CONFIG_SECURITY_NETWORK
- struct list_head unix_stream_connect;
- struct list_head unix_may_send;
- struct list_head socket_create;
- struct list_head socket_post_create;
- struct list_head socket_bind;
- struct list_head socket_connect;
- struct list_head socket_listen;
- struct list_head socket_accept;
- struct list_head socket_sendmsg;
- struct list_head socket_recvmsg;
- struct list_head socket_getsockname;
- struct list_head socket_getpeername;
- struct list_head socket_getsockopt;
- struct list_head socket_setsockopt;
- struct list_head socket_shutdown;
- struct list_head socket_sock_rcv_skb;
- struct list_head socket_getpeersec_stream;
- struct list_head socket_getpeersec_dgram;
- struct list_head sk_alloc_security;
- struct list_head sk_free_security;
- struct list_head sk_clone_security;
- struct list_head sk_getsecid;
- struct list_head sock_graft;
- struct list_head inet_conn_request;
- struct list_head inet_csk_clone;
- struct list_head inet_conn_established;
- struct list_head secmark_relabel_packet;
- struct list_head secmark_refcount_inc;
- struct list_head secmark_refcount_dec;
- struct list_head req_classify_flow;
- struct list_head tun_dev_alloc_security;
- struct list_head tun_dev_free_security;
- struct list_head tun_dev_create;
- struct list_head tun_dev_attach_queue;
- struct list_head tun_dev_attach;
- struct list_head tun_dev_open;
+ LSM_unix_stream_connect,
+ LSM_unix_may_send,
+ LSM_socket_create,
+ LSM_socket_post_create,
+ LSM_socket_bind,
+ LSM_socket_connect,
+ LSM_socket_listen,
+ LSM_socket_accept,
+ LSM_socket_sendmsg,
+ LSM_socket_recvmsg,
+ LSM_socket_getsockname,
+ LSM_socket_getpeername,
+ LSM_socket_getsockopt,
+ LSM_socket_setsockopt,
+ LSM_socket_shutdown,
+ LSM_socket_sock_rcv_skb,
+ LSM_socket_getpeersec_stream,
+ LSM_socket_getpeersec_dgram,
+ LSM_sk_alloc_security,
+ LSM_sk_free_security,
+ LSM_sk_clone_security,
+ LSM_sk_getsecid,
+ LSM_sock_graft,
+ LSM_inet_conn_request,
+ LSM_inet_csk_clone,
+ LSM_inet_conn_established,
+ LSM_secmark_relabel_packet,
+ LSM_secmark_refcount_inc,
+ LSM_secmark_refcount_dec,
+ LSM_req_classify_flow,
+ LSM_tun_dev_alloc_security,
+ LSM_tun_dev_free_security,
+ LSM_tun_dev_create,
+ LSM_tun_dev_attach_queue,
+ LSM_tun_dev_attach,
+ LSM_tun_dev_open,
#endif /* CONFIG_SECURITY_NETWORK */
#ifdef CONFIG_SECURITY_NETWORK_XFRM
- struct list_head xfrm_policy_alloc_security;
- struct list_head xfrm_policy_clone_security;
- struct list_head xfrm_policy_free_security;
- struct list_head xfrm_policy_delete_security;
- struct list_head xfrm_state_alloc;
- struct list_head xfrm_state_alloc_acquire;
- struct list_head xfrm_state_free_security;
- struct list_head xfrm_state_delete_security;
- struct list_head xfrm_policy_lookup;
- struct list_head xfrm_state_pol_flow_match;
- struct list_head xfrm_decode_session;
+ LSM_xfrm_policy_alloc_security,
+ LSM_xfrm_policy_clone_security,
+ LSM_xfrm_policy_free_security,
+ LSM_xfrm_policy_delete_security,
+ LSM_xfrm_state_alloc,
+ LSM_xfrm_state_alloc_acquire,
+ LSM_xfrm_state_free_security,
+ LSM_xfrm_state_delete_security,
+ LSM_xfrm_policy_lookup,
+ LSM_xfrm_state_pol_flow_match,
+ LSM_xfrm_decode_session,
#endif /* CONFIG_SECURITY_NETWORK_XFRM */
#ifdef CONFIG_KEYS
- struct list_head key_alloc;
- struct list_head key_free;
- struct list_head key_permission;
- struct list_head key_getsecurity;
+ LSM_key_alloc,
+ LSM_key_free,
+ LSM_key_permission,
+ LSM_key_getsecurity,
#endif /* CONFIG_KEYS */
#ifdef CONFIG_AUDIT
- struct list_head audit_rule_init;
- struct list_head audit_rule_known;
- struct list_head audit_rule_match;
- struct list_head audit_rule_free;
+ LSM_audit_rule_init,
+ LSM_audit_rule_known,
+ LSM_audit_rule_match,
+ LSM_audit_rule_free,
#endif /* CONFIG_AUDIT */
+ LSM_MAX_HOOK_INDEX
};
/*
@@ -1884,8 +1885,8 @@ struct security_hook_heads {
*/
struct security_hook_list {
struct list_head list;
- struct list_head *head;
union security_list_options hook;
+ enum security_hook_index idx;
char *lsm;
};
@@ -1896,9 +1897,8 @@ struct security_hook_list {
* text involved.
*/
#define LSM_HOOK_INIT(HEAD, HOOK) \
- { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
+ { .idx = LSM_##HEAD, .hook = { .HEAD = HOOK } }
-extern struct security_hook_heads security_hook_heads;
extern char *lsm_names;
extern void security_add_hooks(struct security_hook_list *hooks, int count,
diff --git a/security/security.c b/security/security.c
index 38316bb..c492f68 100644
--- a/security/security.c
+++ b/security/security.c
@@ -33,7 +33,8 @@
/* Maximum number of letters for an LSM name string */
#define SECURITY_NAME_MAX 10
-struct security_hook_heads security_hook_heads __lsm_ro_after_init;
+static struct list_head hook_heads[LSM_MAX_HOOK_INDEX]
+ __lsm_ro_after_init;
char *lsm_names;
/* Boot-time LSM user choice */
static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
@@ -56,12 +57,10 @@ static void __init do_security_initcalls(void)
*/
int __init security_init(void)
{
- int i;
- struct list_head *list = (struct list_head *) &security_hook_heads;
+ enum security_hook_index i;
- for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct list_head);
- i++)
- INIT_LIST_HEAD(&list[i]);
+ for (i = 0; i < LSM_MAX_HOOK_INDEX; i++)
+ INIT_LIST_HEAD(&hook_heads[i]);
pr_info("Security Framework initialized\n");
/*
@@ -158,8 +157,12 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
int i;
for (i = 0; i < count; i++) {
+ enum security_hook_index idx = hooks[i].idx;
+
hooks[i].lsm = lsm;
- list_add_tail_rcu(&hooks[i].list, hooks[i].head);
+ /* Can't hit this BUG_ON() unless LSM_HOOK_INIT() is broken. */
+ BUG_ON(idx < 0 || idx >= LSM_MAX_HOOK_INDEX);
+ list_add_tail_rcu(&hooks[i].list, &hook_heads[idx]);
}
if (lsm_append(lsm, &lsm_names) < 0)
panic("%s - Cannot get early memory.\n", __func__);
@@ -179,7 +182,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
do { \
struct security_hook_list *P; \
\
- list_for_each_entry(P, &security_hook_heads.FUNC, list) \
+ list_for_each_entry(P, &hook_heads[LSM_##FUNC], list) \
P->hook.FUNC(__VA_ARGS__); \
} while (0)
@@ -188,7 +191,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
do { \
struct security_hook_list *P; \
\
- list_for_each_entry(P, &security_hook_heads.FUNC, list) { \
+ list_for_each_entry(P, &hook_heads[LSM_##FUNC], list) { \
RC = P->hook.FUNC(__VA_ARGS__); \
if (RC != 0) \
break; \
@@ -295,7 +298,7 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
* agree that it should be set it will. If any module
* thinks it should not be set it won't.
*/
- list_for_each_entry(hp, &security_hook_heads.vm_enough_memory, list) {
+ list_for_each_entry(hp, &hook_heads[LSM_vm_enough_memory], list) {
rc = hp->hook.vm_enough_memory(mm, pages);
if (rc <= 0) {
cap_sys_admin = 0;
@@ -785,7 +788,7 @@ int security_inode_getsecurity(struct inode *inode, const char *name, void **buf
/*
* Only one module will provide an attribute with a given name.
*/
- list_for_each_entry(hp, &security_hook_heads.inode_getsecurity, list) {
+ list_for_each_entry(hp, &hook_heads[LSM_inode_getsecurity], list) {
rc = hp->hook.inode_getsecurity(inode, name, buffer, alloc);
if (rc != -EOPNOTSUPP)
return rc;
@@ -803,7 +806,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void
/*
* Only one module will provide an attribute with a given name.
*/
- list_for_each_entry(hp, &security_hook_heads.inode_setsecurity, list) {
+ list_for_each_entry(hp, &hook_heads[LSM_inode_setsecurity], list) {
rc = hp->hook.inode_setsecurity(inode, name, value, size,
flags);
if (rc != -EOPNOTSUPP)
@@ -1111,7 +1114,7 @@ int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
int rc = -ENOSYS;
struct security_hook_list *hp;
- list_for_each_entry(hp, &security_hook_heads.task_prctl, list) {
+ list_for_each_entry(hp, &hook_heads[LSM_task_prctl], list) {
thisrc = hp->hook.task_prctl(option, arg2, arg3, arg4, arg5);
if (thisrc != -ENOSYS) {
rc = thisrc;
@@ -1587,7 +1590,7 @@ int security_xfrm_state_pol_flow_match(struct xfrm_state *x,
* For speed optimization, we explicitly break the loop rather than
* using the macro
*/
- list_for_each_entry(hp, &security_hook_heads.xfrm_state_pol_flow_match,
+ list_for_each_entry(hp, &hook_heads[LSM_xfrm_state_pol_flow_match],
list) {
rc = hp->hook.xfrm_state_pol_flow_match(x, xp, fl);
break;
--
2.9.3
The MMU available in many systems runnign Linux can often provide R/O
protection to the memory pages it handles.
However, this works efficiently only when said pages contain only data
that does not need to be modified.
This can work well for statically allocated variables, however it doe
not fit too well the case of dynamically allocated ones.
Dynamic allocation does not provide, currently, means for grouping
variables in memory pages that would contain exclusively data that can
be made read only.
The allocator here provided (pmalloc - protectable memory allocator)
introduces the concept of pools of protectable memory.
A module can request a pool and then refer any allocation request to the
pool handler it has received.
Once all the memory requested (over various iterations) is initialized,
the pool can be protected.
After this point, the pool can only be destroyed (it is up to the module
to avoid any no further references to the memory from the pool, after
the destruction is invoked).
The latter case is mainly meant for releasing memory when a module is
unloaded.
A module can have as many pools as needed, for example to support the
protection of data that is initialized in sufficiently distinct phases.
Signed-off-by: Igor Stoppa <[email protected]>
---
include/linux/page-flags.h | 2 +
include/linux/pmalloc.h | 20 ++++
include/trace/events/mmflags.h | 1 +
mm/Makefile | 2 +-
mm/pmalloc.c | 227 +++++++++++++++++++++++++++++++++++++++++
mm/usercopy.c | 24 +++--
6 files changed, 266 insertions(+), 10 deletions(-)
create mode 100644 include/linux/pmalloc.h
create mode 100644 mm/pmalloc.c
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 6b5818d..acc0723 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -81,6 +81,7 @@ enum pageflags {
PG_active,
PG_waiters, /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
PG_slab,
+ PG_pmalloc,
PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
PG_arch_1,
PG_reserved,
@@ -274,6 +275,7 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
TESTCLEARFLAG(Active, active, PF_HEAD)
__PAGEFLAG(Slab, slab, PF_NO_TAIL)
__PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
+__PAGEFLAG(Pmalloc, pmalloc, PF_NO_TAIL)
PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */
/* Xen */
diff --git a/include/linux/pmalloc.h b/include/linux/pmalloc.h
new file mode 100644
index 0000000..83d3557
--- /dev/null
+++ b/include/linux/pmalloc.h
@@ -0,0 +1,20 @@
+/*
+ * pmalloc.h: Header for Protectable Memory Allocator
+ *
+ * (C) Copyright 2017 Huawei Technologies Co. Ltd.
+ * Author: Igor Stoppa <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#ifndef _PMALLOC_H
+#define _PMALLOC_H
+
+struct pmalloc_pool *pmalloc_create_pool(const char *name);
+void *pmalloc(unsigned long size, struct pmalloc_pool *pool);
+int pmalloc_protect_pool(struct pmalloc_pool *pool);
+int pmalloc_destroy_pool(struct pmalloc_pool *pool);
+#endif
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 304ff94..41d1587 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -91,6 +91,7 @@
{1UL << PG_lru, "lru" }, \
{1UL << PG_active, "active" }, \
{1UL << PG_slab, "slab" }, \
+ {1UL << PG_pmalloc, "pmalloc" }, \
{1UL << PG_owner_priv_1, "owner_priv_1" }, \
{1UL << PG_arch_1, "arch_1" }, \
{1UL << PG_reserved, "reserved" }, \
diff --git a/mm/Makefile b/mm/Makefile
index 026f6a8..79dd99c 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -25,7 +25,7 @@ mmu-y := nommu.o
mmu-$(CONFIG_MMU) := gup.o highmem.o memory.o mincore.o \
mlock.o mmap.o mprotect.o mremap.o msync.o \
page_vma_mapped.o pagewalk.o pgtable-generic.o \
- rmap.o vmalloc.o
+ rmap.o vmalloc.o pmalloc.o
ifdef CONFIG_CROSS_MEMORY_ATTACH
diff --git a/mm/pmalloc.c b/mm/pmalloc.c
new file mode 100644
index 0000000..c73d60c
--- /dev/null
+++ b/mm/pmalloc.c
@@ -0,0 +1,227 @@
+/*
+ * pmalloc.c: Protectable Memory Allocator
+ *
+ * (C) Copyright 2017 Huawei Technologies Co. Ltd.
+ * Author: Igor Stoppa <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include <linux/printk.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/mutex.h>
+#include <linux/atomic.h>
+#include <asm/set_memory.h>
+#include <asm/page.h>
+
+typedef uint64_t align_t;
+#define WORD_SIZE sizeof(align_t)
+
+#define __PMALLOC_ALIGNED __aligned(WORD_SIZE)
+
+#define MAX_POOL_NAME_LEN 40
+
+#define PMALLOC_HASH_SIZE (PAGE_SIZE / 2)
+
+#define PMALLOC_HASH_ENTRIES ilog2(PMALLOC_HASH_SIZE)
+
+
+struct pmalloc_data {
+ struct hlist_head pools_list_head;
+ struct mutex pools_list_mutex;
+ atomic_t pools_count;
+};
+
+struct pmalloc_pool {
+ struct hlist_node pools_list;
+ struct hlist_head nodes_list_head;
+ struct mutex nodes_list_mutex;
+ atomic_t nodes_count;
+ bool protected;
+ char name[MAX_POOL_NAME_LEN];
+};
+
+struct pmalloc_node {
+ struct hlist_node nodes_list;
+ atomic_t used_words;
+ unsigned int total_words;
+ __PMALLOC_ALIGNED align_t data[];
+};
+
+#define HEADER_SIZE sizeof(struct pmalloc_node)
+
+static struct pmalloc_data *pmalloc_data;
+
+struct pmalloc_node *__pmalloc_create_node(int words)
+{
+ struct pmalloc_node *node;
+ unsigned long size, i, pages;
+ struct page *p;
+
+ size = ((HEADER_SIZE - 1 + PAGE_SIZE) +
+ WORD_SIZE * (unsigned long) words) & PAGE_MASK;
+ node = vmalloc(size);
+ if (!node)
+ return NULL;
+ atomic_set(&node->used_words, 0);
+ node->total_words = (size - HEADER_SIZE) / WORD_SIZE;
+ pages = size / PAGE_SIZE;
+ for (i = 0; i < pages; i++) {
+ p = vmalloc_to_page((void *)(i * PAGE_SIZE +
+ (unsigned long)node));
+ __SetPagePmalloc(p);
+ }
+ return node;
+}
+
+void *pmalloc(unsigned long size, struct pmalloc_pool *pool)
+{
+ struct pmalloc_node *node;
+ int req_words;
+ int starting_word;
+
+ if (size > INT_MAX || size == 0)
+ return NULL;
+ req_words = (((int)size) + WORD_SIZE - 1) / WORD_SIZE;
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list) {
+ starting_word = atomic_fetch_add(req_words, &node->used_words);
+ if (starting_word + req_words > node->total_words)
+ atomic_sub(req_words, &node->used_words);
+ else
+ goto found_node;
+ }
+ rcu_read_unlock();
+ node = __pmalloc_create_node(req_words);
+ starting_word = atomic_fetch_add(req_words, &node->used_words);
+ mutex_lock(&pool->nodes_list_mutex);
+ hlist_add_head_rcu(&node->nodes_list, &pool->nodes_list_head);
+ mutex_unlock(&pool->nodes_list_mutex);
+ atomic_inc(&pool->nodes_count);
+found_node:
+ return node->data + starting_word;
+}
+
+const char msg[] = "Not a valid Pmalloc object.";
+const char *__pmalloc_check_object(const void *ptr, unsigned long n)
+{
+ unsigned long p;
+
+ p = (unsigned long)ptr;
+ n += (unsigned long)ptr;
+ for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) {
+ if (is_vmalloc_addr((void *)p)) {
+ struct page *page;
+
+ page = vmalloc_to_page((void *)p);
+ if (!(page && PagePmalloc(page)))
+ return msg;
+ }
+ }
+ return NULL;
+}
+EXPORT_SYMBOL(__pmalloc_check_object);
+
+
+struct pmalloc_pool *pmalloc_create_pool(const char *name)
+{
+ struct pmalloc_pool *pool;
+ unsigned int name_len;
+
+ name_len = strnlen(name, MAX_POOL_NAME_LEN);
+ if (unlikely(name_len == MAX_POOL_NAME_LEN))
+ return NULL;
+ pool = vmalloc(sizeof(struct pmalloc_pool));
+ if (unlikely(!pool))
+ return NULL;
+ INIT_HLIST_NODE(&pool->pools_list);
+ INIT_HLIST_HEAD(&pool->nodes_list_head);
+ mutex_init(&pool->nodes_list_mutex);
+ atomic_set(&pool->nodes_count, 0);
+ pool->protected = false;
+ strcpy(pool->name, name);
+ mutex_lock(&pmalloc_data->pools_list_mutex);
+ hlist_add_head_rcu(&pool->pools_list, &pmalloc_data->pools_list_head);
+ mutex_unlock(&pmalloc_data->pools_list_mutex);
+ atomic_inc(&pmalloc_data->pools_count);
+ return pool;
+}
+
+int pmalloc_protect_pool(struct pmalloc_pool *pool)
+{
+ struct pmalloc_node *node;
+
+ if (!pool)
+ return -EINVAL;
+ mutex_lock(&pool->nodes_list_mutex);
+ hlist_for_each_entry(node, &pool->nodes_list_head, nodes_list) {
+ unsigned long size, pages;
+
+ size = WORD_SIZE * node->total_words + HEADER_SIZE;
+ pages = size / PAGE_SIZE;
+ set_memory_ro((unsigned long)node, pages);
+ }
+ pool->protected = true;
+ mutex_unlock(&pool->nodes_list_mutex);
+ return 0;
+}
+
+static __always_inline
+void __pmalloc_destroy_node(struct pmalloc_node *node)
+{
+ int pages, i;
+
+ pages = (node->total_words * WORD_SIZE + HEADER_SIZE) / PAGE_SIZE;
+ for (i = 0; i < pages; i++)
+ __ClearPagePmalloc(vmalloc_to_page(node + i * PAGE_SIZE));
+ vfree(node);
+}
+
+int pmalloc_destroy_pool(struct pmalloc_pool *pool)
+{
+ struct pmalloc_node *node;
+
+ if (!pool)
+ return -EINVAL;
+ mutex_lock(&pool->nodes_list_mutex);
+ mutex_lock(&pmalloc_data->pools_list_mutex);
+ hlist_del_rcu(&pool->pools_list);
+ mutex_unlock(&pmalloc_data->pools_list_mutex);
+ hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list) {
+ int pages;
+
+ pages = (node->total_words * WORD_SIZE + HEADER_SIZE) /
+ PAGE_SIZE;
+ set_memory_rw((unsigned long)node, pages);
+ }
+
+ while (likely(!hlist_empty(&pool->nodes_list_head))) {
+ node = hlist_entry(pool->nodes_list_head.first,
+ struct pmalloc_node, nodes_list);
+ hlist_del(&node->nodes_list);
+ __pmalloc_destroy_node(node);
+ }
+ mutex_unlock(&pool->nodes_list_mutex);
+ atomic_dec(&pmalloc_data->pools_count);
+ vfree(pool);
+ return 0;
+}
+
+int __init pmalloc_init(void)
+{
+ pmalloc_data = vmalloc(sizeof(struct pmalloc_data));
+ if (!pmalloc_data)
+ return -ENOMEM;
+ INIT_HLIST_HEAD(&pmalloc_data->pools_list_head);
+ mutex_init(&pmalloc_data->pools_list_mutex);
+ atomic_set(&pmalloc_data->pools_count, 0);
+ return 0;
+}
+EXPORT_SYMBOL(pmalloc_init);
diff --git a/mm/usercopy.c b/mm/usercopy.c
index a9852b2..29bb691 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -195,22 +195,28 @@ static inline const char *check_page_span(const void *ptr, unsigned long n,
return NULL;
}
+extern const char *__pmalloc_check_object(const void *ptr, unsigned long n);
+
static inline const char *check_heap_object(const void *ptr, unsigned long n,
bool to_user)
{
struct page *page;
- if (!virt_addr_valid(ptr))
- return NULL;
-
- page = virt_to_head_page(ptr);
-
- /* Check slab allocator for flags and size. */
- if (PageSlab(page))
- return __check_heap_object(ptr, n, page);
+ if (virt_addr_valid(ptr)) {
+ page = virt_to_head_page(ptr);
+ /* Check slab allocator for flags and size. */
+ if (PageSlab(page))
+ return __check_heap_object(ptr, n, page);
/* Verify object does not incorrectly span multiple pages. */
- return check_page_span(ptr, n, page, to_user);
+ return check_page_span(ptr, n, page, to_user);
+ }
+ if (likely(is_vmalloc_addr(ptr))) {
+ page = vmalloc_to_page(ptr);
+ if (unlikely(page && PagePmalloc(page)))
+ return __pmalloc_check_object(ptr, n);
+ }
+ return NULL;
}
/*
--
2.9.3
This patch shows how it is possible to take advantage of pmalloc:
instead of using the build-time option __lsm_ro_after_init, to decide if
it is possible to keep the hooks modifiable, now this becomes a
boot-time decision, based on the kernel command line.
This patch relies on:
"Convert security_hook_heads into explicit array of struct list_head"
Author: Tetsuo Handa <[email protected]>
to break free from the static constraint imposed by the previous
hardening model, based on __ro_after_init.
Signed-off-by: Igor Stoppa <[email protected]>
CC: Tetsuo Handa <[email protected]>
---
init/main.c | 2 ++
security/security.c | 29 ++++++++++++++++++++++++++---
2 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/init/main.c b/init/main.c
index f866510..7850887 100644
--- a/init/main.c
+++ b/init/main.c
@@ -485,6 +485,7 @@ static void __init mm_init(void)
ioremap_huge_init();
}
+extern int __init pmalloc_init(void);
asmlinkage __visible void __init start_kernel(void)
{
char *command_line;
@@ -653,6 +654,7 @@ asmlinkage __visible void __init start_kernel(void)
proc_caches_init();
buffer_init();
key_init();
+ pmalloc_init();
security_init();
dbg_late_init();
vfs_caches_init();
diff --git a/security/security.c b/security/security.c
index c492f68..4285545 100644
--- a/security/security.c
+++ b/security/security.c
@@ -26,6 +26,7 @@
#include <linux/personality.h>
#include <linux/backing-dev.h>
#include <linux/string.h>
+#include <linux/pmalloc.h>
#include <net/flow.h>
#define MAX_LSM_EVM_XATTR 2
@@ -33,8 +34,17 @@
/* Maximum number of letters for an LSM name string */
#define SECURITY_NAME_MAX 10
-static struct list_head hook_heads[LSM_MAX_HOOK_INDEX]
- __lsm_ro_after_init;
+static int security_debug;
+
+static __init int set_security_debug(char *str)
+{
+ get_option(&str, &security_debug);
+ return 0;
+}
+early_param("security_debug", set_security_debug);
+
+static struct list_head *hook_heads;
+static struct pmalloc_pool *sec_pool;
char *lsm_names;
/* Boot-time LSM user choice */
static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
@@ -59,6 +69,13 @@ int __init security_init(void)
{
enum security_hook_index i;
+ sec_pool = pmalloc_create_pool("security");
+ if (!sec_pool)
+ goto error_pool;
+ hook_heads = pmalloc(sizeof(struct list_head) * LSM_MAX_HOOK_INDEX,
+ sec_pool);
+ if (!hook_heads)
+ goto error_heads;
for (i = 0; i < LSM_MAX_HOOK_INDEX; i++)
INIT_LIST_HEAD(&hook_heads[i]);
pr_info("Security Framework initialized\n");
@@ -74,8 +91,14 @@ int __init security_init(void)
* Load all the remaining security modules.
*/
do_security_initcalls();
-
+ if (!security_debug)
+ pmalloc_protect_pool(sec_pool);
return 0;
+
+error_heads:
+ pmalloc_destroy_pool(sec_pool);
+error_pool:
+ return -ENOMEM;
}
/* Save user chosen LSM */
--
2.9.3
Debugfs interface: it creates a file
/sys/kernel/debug/pmalloc/pools
which exposes statistics about all the pools and memory nodes in use.
Signed-off-by: Igor Stoppa <[email protected]>
---
mm/Kconfig | 11 ++++++
mm/pmalloc.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 124 insertions(+)
diff --git a/mm/Kconfig b/mm/Kconfig
index beb7a45..dfbdc07 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -539,6 +539,17 @@ config CMA_AREAS
If unsure, leave the default value "7".
+config PMALLOC_DEBUG
+ bool "Protectable Memory Allocator debugging"
+ depends on DEBUG_KERNEL
+ default y
+ help
+ Debugfs support for dumping information about memory pools.
+ It shows internal stats: free/used/total space, protection
+ status, data overhead, etc.
+
+ If unsure, say "y".
+
config MEM_SOFT_DIRTY
bool "Track memory changes"
depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
diff --git a/mm/pmalloc.c b/mm/pmalloc.c
index c73d60c..6dd6bbe 100644
--- a/mm/pmalloc.c
+++ b/mm/pmalloc.c
@@ -225,3 +225,116 @@ int __init pmalloc_init(void)
return 0;
}
EXPORT_SYMBOL(pmalloc_init);
+
+#ifdef CONFIG_PMALLOC_DEBUG
+#include <linux/debugfs.h>
+static struct dentry *pmalloc_root;
+
+static void *__pmalloc_seq_start(struct seq_file *s, loff_t *pos)
+{
+ if (*pos)
+ return NULL;
+ return pos;
+}
+
+static void *__pmalloc_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ return NULL;
+}
+
+static void __pmalloc_seq_stop(struct seq_file *s, void *v)
+{
+}
+
+static __always_inline
+void __seq_printf_node(struct seq_file *s, struct pmalloc_node *node)
+{
+ unsigned long total_space, node_pages, end_of_node,
+ used_space, available_space;
+ int total_words, used_words, available_words;
+
+ used_words = atomic_read(&node->used_words);
+ total_words = node->total_words;
+ available_words = total_words - used_words;
+ used_space = used_words * WORD_SIZE;
+ total_space = total_words * WORD_SIZE;
+ available_space = total_space - used_space;
+ node_pages = (total_space + HEADER_SIZE) / PAGE_SIZE;
+ end_of_node = total_space + HEADER_SIZE + (unsigned long) node;
+ seq_printf(s, " - node:\t\t%p\n", node);
+ seq_printf(s, " - start of data ptr:\t%p\n", node->data);
+ seq_printf(s, " - end of node ptr:\t%p\n", (void *)end_of_node);
+ seq_printf(s, " - total words:\t%d\n", total_words);
+ seq_printf(s, " - used words:\t%d\n", used_words);
+ seq_printf(s, " - available words:\t%d\n", available_words);
+ seq_printf(s, " - pages:\t\t%lu\n", node_pages);
+ seq_printf(s, " - total space:\t%lu\n", total_space);
+ seq_printf(s, " - used space:\t%lu\n", used_space);
+ seq_printf(s, " - available space:\t%lu\n", available_space);
+}
+
+static __always_inline
+void __seq_printf_pool(struct seq_file *s, struct pmalloc_pool *pool)
+{
+ struct pmalloc_node *node;
+
+ seq_printf(s, "pool:\t\t\t%p\n", pool);
+ seq_printf(s, " - name:\t\t%s\n", pool->name);
+ seq_printf(s, " - protected:\t\t%u\n", pool->protected);
+ seq_printf(s, " - nodes count:\t\t%u\n",
+ atomic_read(&pool->nodes_count));
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list)
+ __seq_printf_node(s, node);
+ rcu_read_unlock();
+}
+
+static int __pmalloc_seq_show(struct seq_file *s, void *v)
+{
+ struct pmalloc_pool *pool;
+
+ seq_printf(s, "pools count:\t\t%u\n",
+ atomic_read(&pmalloc_data->pools_count));
+ seq_printf(s, "page size:\t\t%lu\n", PAGE_SIZE);
+ seq_printf(s, "word size:\t\t%lu\n", WORD_SIZE);
+ seq_printf(s, "node header size:\t%lu\n", HEADER_SIZE);
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(pool, &pmalloc_data->pools_list_head,
+ pools_list)
+ __seq_printf_pool(s, pool);
+ rcu_read_unlock();
+ return 0;
+}
+
+static const struct seq_operations pmalloc_seq_ops = {
+ .start = __pmalloc_seq_start,
+ .next = __pmalloc_seq_next,
+ .stop = __pmalloc_seq_stop,
+ .show = __pmalloc_seq_show,
+};
+
+static int __pmalloc_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &pmalloc_seq_ops);
+}
+
+static const struct file_operations pmalloc_file_ops = {
+ .owner = THIS_MODULE,
+ .open = __pmalloc_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release
+};
+
+
+static int __init __pmalloc_init_track_pool(void)
+{
+ struct dentry *de = NULL;
+
+ pmalloc_root = debugfs_create_dir("pmalloc", NULL);
+ debugfs_create_file("pools", 0644, pmalloc_root, NULL,
+ &pmalloc_file_ops);
+ return 0;
+}
+late_initcall(__pmalloc_init_track_pool);
+#endif
--
2.9.3
On 6/5/2017 12:22 PM, Igor Stoppa wrote:
> This patch shows how it is possible to take advantage of pmalloc:
> instead of using the build-time option __lsm_ro_after_init, to decide if
> it is possible to keep the hooks modifiable, now this becomes a
> boot-time decision, based on the kernel command line.
>
> This patch relies on:
>
> "Convert security_hook_heads into explicit array of struct list_head"
> Author: Tetsuo Handa <[email protected]>
>
> to break free from the static constraint imposed by the previous
> hardening model, based on __ro_after_init.
>
> Signed-off-by: Igor Stoppa <[email protected]>
> CC: Tetsuo Handa <[email protected]>
> ---
> init/main.c | 2 ++
> security/security.c | 29 ++++++++++++++++++++++++++---
> 2 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/init/main.c b/init/main.c
> index f866510..7850887 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -485,6 +485,7 @@ static void __init mm_init(void)
> ioremap_huge_init();
> }
>
> +extern int __init pmalloc_init(void);
> asmlinkage __visible void __init start_kernel(void)
> {
> char *command_line;
> @@ -653,6 +654,7 @@ asmlinkage __visible void __init start_kernel(void)
> proc_caches_init();
> buffer_init();
> key_init();
> + pmalloc_init();
> security_init();
> dbg_late_init();
> vfs_caches_init();
> diff --git a/security/security.c b/security/security.c
> index c492f68..4285545 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -26,6 +26,7 @@
> #include <linux/personality.h>
> #include <linux/backing-dev.h>
> #include <linux/string.h>
> +#include <linux/pmalloc.h>
> #include <net/flow.h>
>
> #define MAX_LSM_EVM_XATTR 2
> @@ -33,8 +34,17 @@
> /* Maximum number of letters for an LSM name string */
> #define SECURITY_NAME_MAX 10
>
> -static struct list_head hook_heads[LSM_MAX_HOOK_INDEX]
> - __lsm_ro_after_init;
> +static int security_debug;
> +
> +static __init int set_security_debug(char *str)
> +{
> + get_option(&str, &security_debug);
> + return 0;
> +}
> +early_param("security_debug", set_security_debug);
I don't care for calling this "security debug". Making
the lists writable after init isn't about development,
it's about (Tetsuo's desire for) dynamic module loading.
I would prefer "dynamic_module_lists" our something else
more descriptive.
> +
> +static struct list_head *hook_heads;
> +static struct pmalloc_pool *sec_pool;
> char *lsm_names;
> /* Boot-time LSM user choice */
> static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
> @@ -59,6 +69,13 @@ int __init security_init(void)
> {
> enum security_hook_index i;
>
> + sec_pool = pmalloc_create_pool("security");
> + if (!sec_pool)
> + goto error_pool;
Excessive gotoing - return -ENOMEM instead.
> + hook_heads = pmalloc(sizeof(struct list_head) * LSM_MAX_HOOK_INDEX,
> + sec_pool);
> + if (!hook_heads)
> + goto error_heads;
This is the only case where you'd destroy the pool, so
the goto is unnecessary. Put the
pmalloc_destroy_pool(sec_pool);
return -ENOMEM;
under the if here.
> for (i = 0; i < LSM_MAX_HOOK_INDEX; i++)
> INIT_LIST_HEAD(&hook_heads[i]);
> pr_info("Security Framework initialized\n");
> @@ -74,8 +91,14 @@ int __init security_init(void)
> * Load all the remaining security modules.
> */
> do_security_initcalls();
> -
> + if (!security_debug)
> + pmalloc_protect_pool(sec_pool);
> return 0;
> +
> +error_heads:
> + pmalloc_destroy_pool(sec_pool);
> +error_pool:
> + return -ENOMEM;
> }
>
> /* Save user chosen LSM */
On Mon, Jun 5, 2017 at 9:22 PM, Igor Stoppa <[email protected]> wrote:
> Debugfs interface: it creates a file
>
> /sys/kernel/debug/pmalloc/pools
>
> which exposes statistics about all the pools and memory nodes in use.
>
> Signed-off-by: Igor Stoppa <[email protected]>
[...]
> + seq_printf(s, " - node:\t\t%p\n", node);
> + seq_printf(s, " - start of data ptr:\t%p\n", node->data);
> + seq_printf(s, " - end of node ptr:\t%p\n", (void *)end_of_node);
[...]
> + seq_printf(s, "pool:\t\t\t%p\n", pool);
[...]
> + debugfs_create_file("pools", 0644, pmalloc_root, NULL,
> + &pmalloc_file_ops);
You should probably be using %pK to hide the kernel pointers.
Casey Schaufler wrote:
> > @@ -33,8 +34,17 @@
> > /* Maximum number of letters for an LSM name string */
> > #define SECURITY_NAME_MAX 10
> >
> > -static struct list_head hook_heads[LSM_MAX_HOOK_INDEX]
> > - __lsm_ro_after_init;
> > +static int security_debug;
> > +
> > +static __init int set_security_debug(char *str)
> > +{
> > + get_option(&str, &security_debug);
> > + return 0;
> > +}
> > +early_param("security_debug", set_security_debug);
>
> I don't care for calling this "security debug". Making
> the lists writable after init isn't about development,
> it's about (Tetsuo's desire for) dynamic module loading.
> I would prefer "dynamic_module_lists" our something else
> more descriptive.
Maybe dynamic_lsm ?
>
> > +
> > +static struct list_head *hook_heads;
> > +static struct pmalloc_pool *sec_pool;
> > char *lsm_names;
> > /* Boot-time LSM user choice */
> > static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
> > @@ -59,6 +69,13 @@ int __init security_init(void)
> > {
> > enum security_hook_index i;
> >
> > + sec_pool = pmalloc_create_pool("security");
> > + if (!sec_pool)
> > + goto error_pool;
>
> Excessive gotoing - return -ENOMEM instead.
But does it make sense to continue?
hook_heads == NULL and we will oops as soon as
call_void_hook() or call_int_hook() is called for the first time.
Igor Stoppa wrote:
> +int pmalloc_protect_pool(struct pmalloc_pool *pool)
> +{
> + struct pmalloc_node *node;
> +
> + if (!pool)
> + return -EINVAL;
> + mutex_lock(&pool->nodes_list_mutex);
> + hlist_for_each_entry(node, &pool->nodes_list_head, nodes_list) {
> + unsigned long size, pages;
> +
> + size = WORD_SIZE * node->total_words + HEADER_SIZE;
> + pages = size / PAGE_SIZE;
> + set_memory_ro((unsigned long)node, pages);
> + }
> + pool->protected = true;
> + mutex_unlock(&pool->nodes_list_mutex);
> + return 0;
> +}
As far as I know, not all CONFIG_MMU=y architectures provide
set_memory_ro()/set_memory_rw(). You need to provide fallback for
architectures which do not provide set_memory_ro()/set_memory_rw()
or kernels built with CONFIG_MMU=n.
> mmu-$(CONFIG_MMU) := gup.o highmem.o memory.o mincore.o \
> mlock.o mmap.o mprotect.o mremap.o msync.o \
> page_vma_mapped.o pagewalk.o pgtable-generic.o \
> - rmap.o vmalloc.o
> + rmap.o vmalloc.o pmalloc.o
Is this __PMALLOC_ALIGNED needed? Why not use "long" and "BITS_PER_LONG" ?
> +struct pmalloc_node {
> + struct hlist_node nodes_list;
> + atomic_t used_words;
> + unsigned int total_words;
> + __PMALLOC_ALIGNED align_t data[];
> +};
Please use macros for round up/down.
> + size = ((HEADER_SIZE - 1 + PAGE_SIZE) +
> + WORD_SIZE * (unsigned long) words) & PAGE_MASK;
> + req_words = (((int)size) + WORD_SIZE - 1) / WORD_SIZE;
You need to check for node != NULL before dereference it.
Also, why rcu_read_lock()/rcu_read_unlock() ?
I can't find corresponding synchronize_rcu() etc. in this patch.
pmalloc() won't be hotpath. Enclosing whole using a mutex might be OK.
If any reason to use rcu, rcu_read_unlock() is missing if came from "goto".
+void *pmalloc(unsigned long size, struct pmalloc_pool *pool)
+{
+ struct pmalloc_node *node;
+ int req_words;
+ int starting_word;
+
+ if (size > INT_MAX || size == 0)
+ return NULL;
+ req_words = (((int)size) + WORD_SIZE - 1) / WORD_SIZE;
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list) {
+ starting_word = atomic_fetch_add(req_words, &node->used_words);
+ if (starting_word + req_words > node->total_words)
+ atomic_sub(req_words, &node->used_words);
+ else
+ goto found_node;
+ }
+ rcu_read_unlock();
+ node = __pmalloc_create_node(req_words);
+ starting_word = atomic_fetch_add(req_words, &node->used_words);
+ mutex_lock(&pool->nodes_list_mutex);
+ hlist_add_head_rcu(&node->nodes_list, &pool->nodes_list_head);
+ mutex_unlock(&pool->nodes_list_mutex);
+ atomic_inc(&pool->nodes_count);
+found_node:
+ return node->data + starting_word;
+}
I feel that n is off-by-one if (ptr + n) % PAGE_SIZE == 0
according to check_page_span().
> +const char *__pmalloc_check_object(const void *ptr, unsigned long n)
> +{
> + unsigned long p;
> +
> + p = (unsigned long)ptr;
> + n += (unsigned long)ptr;
> + for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) {
> + if (is_vmalloc_addr((void *)p)) {
> + struct page *page;
> +
> + page = vmalloc_to_page((void *)p);
> + if (!(page && PagePmalloc(page)))
> + return msg;
> + }
> + }
> + return NULL;
> +}
Why need to call pmalloc_init() from loadable kernel module?
It has to be called very early stage of boot for only once.
> +int __init pmalloc_init(void)
> +{
> + pmalloc_data = vmalloc(sizeof(struct pmalloc_data));
> + if (!pmalloc_data)
> + return -ENOMEM;
> + INIT_HLIST_HEAD(&pmalloc_data->pools_list_head);
> + mutex_init(&pmalloc_data->pools_list_mutex);
> + atomic_set(&pmalloc_data->pools_count, 0);
> + return 0;
> +}
> +EXPORT_SYMBOL(pmalloc_init);
Since pmalloc_data is a globally shared variable, why need to
allocate it dynamically? If it is for randomizing the address
of pmalloc_data, it does not make sense to continue because
vmalloc() failure causes subsequent oops.
On Tue, Jun 06, 2017 at 01:44:32PM +0900, Tetsuo Handa wrote:
> Igor Stoppa wrote:
> > +int pmalloc_protect_pool(struct pmalloc_pool *pool)
> > +{
> > + struct pmalloc_node *node;
> > +
> > + if (!pool)
> > + return -EINVAL;
> > + mutex_lock(&pool->nodes_list_mutex);
> > + hlist_for_each_entry(node, &pool->nodes_list_head, nodes_list) {
> > + unsigned long size, pages;
> > +
> > + size = WORD_SIZE * node->total_words + HEADER_SIZE;
> > + pages = size / PAGE_SIZE;
> > + set_memory_ro((unsigned long)node, pages);
> > + }
> > + pool->protected = true;
> > + mutex_unlock(&pool->nodes_list_mutex);
> > + return 0;
> > +}
>
> As far as I know, not all CONFIG_MMU=y architectures provide
> set_memory_ro()/set_memory_rw(). You need to provide fallback for
> architectures which do not provide set_memory_ro()/set_memory_rw()
> or kernels built with CONFIG_MMU=n.
I think we'll just need to generalize CONFIG_STRICT_MODULE_RWX and/or
ARCH_HAS_STRICT_MODULE_RWX so there is a symbol to key this off.
On 05/06/17 23:50, Tetsuo Handa wrote:
> Casey Schaufler wrote:
[...]
>> I don't care for calling this "security debug". Making
>> the lists writable after init isn't about development,
>> it's about (Tetsuo's desire for) dynamic module loading.
>> I would prefer "dynamic_module_lists" our something else
>> more descriptive.
>
> Maybe dynamic_lsm ?
ok, apologies for misunderstanding, I'll fix it.
I am not sure I understood what exactly the use case is:
-1) loading off-tree modules
-2) loading and unloading modules
-3) something else ?
I'm asking this because I now wonder if I should provide means for
protecting the heads later on (which still can make sense for case 1).
Or if it's expected that things will stay fluid and this dynamic loading
is matched by unloading, therefore the heads must stay writable (case 2)
[...]
>>> + if (!sec_pool)
>>> + goto error_pool;
>>
>> Excessive gotoing - return -ENOMEM instead.
>
> But does it make sense to continue?
> hook_heads == NULL and we will oops as soon as
> call_void_hook() or call_int_hook() is called for the first time.
Shouldn't the caller check for result? -ENOMEM gives it a chance to do
so. I can replace the goto.
---
igor
On 05/06/17 23:24, Jann Horn wrote:
> On Mon, Jun 5, 2017 at 9:22 PM, Igor Stoppa <[email protected]> wrote:
>> Debugfs interface: it creates a file
[...]
> You should probably be using %pK to hide the kernel pointers.
ok, will do
---
igor
Igor Stoppa wrote:
> On 05/06/17 23:50, Tetsuo Handa wrote:
> > Casey Schaufler wrote:
>
> [...]
>
> >> I don't care for calling this "security debug". Making
> >> the lists writable after init isn't about development,
> >> it's about (Tetsuo's desire for) dynamic module loading.
> >> I would prefer "dynamic_module_lists" our something else
> >> more descriptive.
> >
> > Maybe dynamic_lsm ?
>
> ok, apologies for misunderstanding, I'll fix it.
>
> I am not sure I understood what exactly the use case is:
> -1) loading off-tree modules
Does off-tree mean out-of-tree? If yes, this case is not correct.
"Loading modules which are not compiled as built-in" is correct.
My use case is to allow users to use LSM modules as loadable kernel
modules which distributors do not compile as built-in.
> -2) loading and unloading modules
Unloading LSM modules is dangerous. Only SELinux allows unloading
at the risk of triggering an oops. If we insert delay while removing
list elements, we can easily observe oops due to free function being
called without corresponding allocation function.
> -3) something else ?
Nothing else, as far as I know.
>
> I'm asking this because I now wonder if I should provide means for
> protecting the heads later on (which still can make sense for case 1).
>
> Or if it's expected that things will stay fluid and this dynamic loading
> is matched by unloading, therefore the heads must stay writable (case 2)
>
> [...]
>
> >>> + if (!sec_pool)
> >>> + goto error_pool;
> >>
> >> Excessive gotoing - return -ENOMEM instead.
> >
> > But does it make sense to continue?
> > hook_heads == NULL and we will oops as soon as
> > call_void_hook() or call_int_hook() is called for the first time.
>
> Shouldn't the caller check for result? -ENOMEM gives it a chance to do
> so. I can replace the goto.
security_init() is called from start_kernel() in init/main.c , and
errors are silently ignored. Thus, I don't think returning error to
the caller makes sense.
On 06/06/17 13:54, Tetsuo Handa wrote:
[...]
> "Loading modules which are not compiled as built-in" is correct.
> My use case is to allow users to use LSM modules as loadable kernel
> modules which distributors do not compile as built-in.
Ok, so I suppose someone should eventually lock down the header, after
the additional modules are loaded.
Who decides when enough is enough, meaning that all the needed modules
are loaded?
Should I provide an interface to user-space? A sysfs entry?
[...]
> Unloading LSM modules is dangerous. Only SELinux allows unloading
> at the risk of triggering an oops. If we insert delay while removing
> list elements, we can easily observe oops due to free function being
> called without corresponding allocation function.
Ok. But even in this case, the sys proposal would still work.
It would just stay unused.
--
igor
On 06/06/17 09:25, Christoph Hellwig wrote:
> On Tue, Jun 06, 2017 at 01:44:32PM +0900, Tetsuo Handa wrote:
[..]
>> As far as I know, not all CONFIG_MMU=y architectures provide
>> set_memory_ro()/set_memory_rw(). You need to provide fallback for
>> architectures which do not provide set_memory_ro()/set_memory_rw()
>> or kernels built with CONFIG_MMU=n.
>
> I think we'll just need to generalize CONFIG_STRICT_MODULE_RWX and/or
> ARCH_HAS_STRICT_MODULE_RWX so there is a symbol to key this off.
Would STRICT_KERNEL_RWX work? It's already present.
If both kernel text and rodata can be protected, so can pmalloc data.
---
igor
Igor Stoppa wrote:
> Who decides when enough is enough, meaning that all the needed modules
> are loaded?
> Should I provide an interface to user-space? A sysfs entry?
No such interface is needed. Just an API for applying set_memory_rw()
and set_memory_ro() on LSM hooks is enough.
security_add_hooks() can call set_memory_rw() before adding hooks and
call set_memory_ro() after adding hooks. Ditto for security_delete_hooks()
for SELinux's unregistration.
Hi,
thanks a lot for the review. My answers are in-line below.
I have rearranged your comments because I wasn't sure how to reply to
them inlined.
On 06/06/17 07:44, Tetsuo Handa wrote:
> Igor Stoppa wrote:
[...]
> As far as I know, not all CONFIG_MMU=y architectures provide
> set_memory_ro()/set_memory_rw().
I'll follow up on this in the existing separate thread.
[...]
>> +struct pmalloc_node {
>> + struct hlist_node nodes_list;
>> + atomic_t used_words;
>> + unsigned int total_words;
>> + __PMALLOC_ALIGNED align_t data[];
>> +};
>
> Is this __PMALLOC_ALIGNED needed? Why not use "long" and "BITS_PER_LONG" ?
In an earlier version I actually asked the same question.
It is currently there because I just don't know enough about various
architectures. The idea of having "align_t" was that it could be tied
into what is the most desirable alignment for each architecture.
But I'm actually looking for advise on this.
>> + size = ((HEADER_SIZE - 1 + PAGE_SIZE) +
>> + WORD_SIZE * (unsigned long) words) & PAGE_MASK;
>
>> + req_words = (((int)size) + WORD_SIZE - 1) / WORD_SIZE;
>
> Please use macros for round up/down.
ok
[...]
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(node, &pool->nodes_list_head, nodes_list) {
> + starting_word = atomic_fetch_add(req_words, &node->used_words);
> + if (starting_word + req_words > node->total_words)
> + atomic_sub(req_words, &node->used_words);
> + else
> + goto found_node;
> + }
> + rcu_read_unlock();
>
> You need to check for node != NULL before dereference it.
This was intentionally left out, on the ground that I'm using the kernel
macros for both populating and walking the list.
So, if I understood correctly, there shouldn't be a case where node is
NULL, right?
Unless it has been tampered/damaged. Is that what you mean?
> Also, why rcu_read_lock()/rcu_read_unlock() ?
> I can't find corresponding synchronize_rcu() etc. in this patch.
oops. Thanks for spotting it.
> pmalloc() won't be hotpath. Enclosing whole using a mutex might be OK.
> If any reason to use rcu, rcu_read_unlock() is missing if came from "goto".
If there are no strong objections, I'd rather fix it and keep it as RCU.
Kees Cook was mentioning the possibility of implementing also
"write seldom" in a similar fashion.
In that case the path is likely to warm up.
It might be premature optimization, but I'd prefer to avoid knowingly
introduce performance issues.
Said this, I agree on the bug you spotted.
>> +const char *__pmalloc_check_object(const void *ptr, unsigned long n)
>> +{
>> + unsigned long p;
>> +
>> + p = (unsigned long)ptr;
>> + n += (unsigned long)ptr;
>> + for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) {
>> + if (is_vmalloc_addr((void *)p)) {
>> + struct page *page;
>> +
>> + page = vmalloc_to_page((void *)p);
>> + if (!(page && PagePmalloc(page)))
>> + return msg;
>> + }
>> + }
>> + return NULL;
>> +}
>
> I feel that n is off-by-one if (ptr + n) % PAGE_SIZE == 0
> according to check_page_span().
Hmm,
let's say PAGE_SIZE is 0x0100 and PAGE MASK 0xFF00
Here are some cases (N = number of pages found):
ptr ptr + n Pages Test N
0x0005 0x00FF 1 0x0000 <= 0x00FF true 1
0x0105 0x00FF 0x0100 <= 0x00FF false 1
0x0005 0x0100 2 0x0000 <= 0x0100 true 1
0x0100 0x0100 0x0100 <= 0x0100 true 2
0x0200 0x0100 0x0200 <= 0x0100 false 2
0x0005 0x01FF 2 0x0000 <= 0x0100 true 1
0x0105 0x01FF 0x0100 <= 0x0100 true 2
0x0205 0x01FF 0x0200 <= 0x0100 false 2
It seems to work. If I am missing your point, could you please
use the same format of the example I made, to explain me?
I might be able to understand better.
>> +int __init pmalloc_init(void)
>> +{
>> + pmalloc_data = vmalloc(sizeof(struct pmalloc_data));
>> + if (!pmalloc_data)
>> + return -ENOMEM;
>> + INIT_HLIST_HEAD(&pmalloc_data->pools_list_head);
>> + mutex_init(&pmalloc_data->pools_list_mutex);
>> + atomic_set(&pmalloc_data->pools_count, 0);
>> + return 0;
>> +}
>> +EXPORT_SYMBOL(pmalloc_init);
>
> Why need to call pmalloc_init() from loadable kernel module?
> It has to be called very early stage of boot for only once.
Yes, this is a bug.
Actually I forgot to put in this patch the real call to pmalloc init,
which is in init/main.c, right before the security init.
I should see if I can move it higher, to allow for more early users of
pmalloc.
> Since pmalloc_data is a globally shared variable, why need to
> allocate it dynamically? If it is for randomizing the address
> of pmalloc_data, it does not make sense to continue because
> vmalloc() failure causes subsequent oops.
My idea was to delegate the failure-handling to the caller, which might
be able to take more sensible actions than what I can do in this function.
I see you have already replied in a different thread that the value is
not checked. So I will remove it.
thanks again for the feedback,
igor
Igor Stoppa wrote:
> >> +struct pmalloc_node {
> >> + struct hlist_node nodes_list;
> >> + atomic_t used_words;
> >> + unsigned int total_words;
> >> + __PMALLOC_ALIGNED align_t data[];
> >> +};
> >
> > Is this __PMALLOC_ALIGNED needed? Why not use "long" and "BITS_PER_LONG" ?
>
> In an earlier version I actually asked the same question.
> It is currently there because I just don't know enough about various
> architectures. The idea of having "align_t" was that it could be tied
> into what is the most desirable alignment for each architecture.
> But I'm actually looking for advise on this.
I think that let the compiler use natural alignment is OK.
> > You need to check for node != NULL before dereference it.
>
> So, if I understood correctly, there shouldn't be a case where node is
> NULL, right?
> Unless it has been tampered/damaged. Is that what you mean?
I meant to say
+ node = __pmalloc_create_node(req_words);
// this location.
+ starting_word = atomic_fetch_add(req_words, &node->used_words);
> >> +const char *__pmalloc_check_object(const void *ptr, unsigned long n)
> >> +{
> >> + unsigned long p;
> >> +
> >> + p = (unsigned long)ptr;
> >> + n += (unsigned long)ptr;
> >> + for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) {
> >> + if (is_vmalloc_addr((void *)p)) {
> >> + struct page *page;
> >> +
> >> + page = vmalloc_to_page((void *)p);
> >> + if (!(page && PagePmalloc(page)))
> >> + return msg;
> >> + }
> >> + }
> >> + return NULL;
> >> +}
> >
> > I feel that n is off-by-one if (ptr + n) % PAGE_SIZE == 0
> > according to check_page_span().
>
> It seems to work. If I am missing your point, could you please
> use the same format of the example I made, to explain me?
If ptr == NULL and n == PAGE_SIZE so that (ptr + n) % PAGE_SIZE == 0,
this loop will access two pages (one page containing p == 0 and another
page containing p == PAGE_SIZE) when this loop should access only one
page containing p == 0. When checking n bytes, it's range is 0 to n - 1.
On 06/06/17 14:42, Tetsuo Handa wrote:
> Igor Stoppa wrote:
>> Who decides when enough is enough, meaning that all the needed modules
>> are loaded?
>> Should I provide an interface to user-space? A sysfs entry?
>
> No such interface is needed. Just an API for applying set_memory_rw()
> and set_memory_ro() on LSM hooks is enough.
>
> security_add_hooks() can call set_memory_rw() before adding hooks and
> call set_memory_ro() after adding hooks. Ditto for security_delete_hooks()
> for SELinux's unregistration.
I think this should be considered part of the 2nd phase "write seldom",
as we agreed with Kees Cook.
Right now the goal was to provide the basic API for:
- create pool
- get memory from pool
- lock the pool
- destroy the pool
And, behind the scene, verify that a memory range falls into Pmalloc pages.
Then would come the "write seldom" part.
The reason for this is that a proper implementation of write seldom
should, imho, make writable only those pages that really need to be
modified. Possibly also add some verification on the call stack about
who is requesting the unlocking.
Therefore I would feel more comfortable in splitting the work into 2 part.
For the case at hand, would it work if there was a non-API call that you
could use until the API is properly expanded?
--
igor
On 06/06/17 15:08, Tetsuo Handa wrote:
> Igor Stoppa wrote:
>>>> +struct pmalloc_node {
>>>> + struct hlist_node nodes_list;
>>>> + atomic_t used_words;
>>>> + unsigned int total_words;
>>>> + __PMALLOC_ALIGNED align_t data[];
>>>> +};
>>>
>>> Is this __PMALLOC_ALIGNED needed? Why not use "long" and "BITS_PER_LONG" ?
>>
>> In an earlier version I actually asked the same question.
>> It is currently there because I just don't know enough about various
>> architectures. The idea of having "align_t" was that it could be tied
>> into what is the most desirable alignment for each architecture.
>> But I'm actually looking for advise on this.
>
> I think that let the compiler use natural alignment is OK.
On a 64 bit machine the preferred alignment might be either 32 or 64,
depending on the application. How can the compiler choose?
>>> You need to check for node != NULL before dereference it.
>>
>> So, if I understood correctly, there shouldn't be a case where node is
>> NULL, right?
>> Unless it has been tampered/damaged. Is that what you mean?
>
> I meant to say
>
> + node = __pmalloc_create_node(req_words);
> // this location.
> + starting_word = atomic_fetch_add(req_words, &node->used_words);
argh, yes
>>>> +const char *__pmalloc_check_object(const void *ptr, unsigned long n)
>>>> +{
>>>> + unsigned long p;
>>>> +
>>>> + p = (unsigned long)ptr;
>>>> + n += (unsigned long)ptr;
>>>> + for (; (PAGE_MASK & p) <= (PAGE_MASK & n); p += PAGE_SIZE) {
>>>> + if (is_vmalloc_addr((void *)p)) {
>>>> + struct page *page;
>>>> +
>>>> + page = vmalloc_to_page((void *)p);
>>>> + if (!(page && PagePmalloc(page)))
>>>> + return msg;
>>>> + }
>>>> + }
>>>> + return NULL;
>>>> +}
>>>
>>> I feel that n is off-by-one if (ptr + n) % PAGE_SIZE == 0
>>> according to check_page_span().
>>
>> It seems to work. If I am missing your point, could you please
>> use the same format of the example I made, to explain me?
>
> If ptr == NULL and n == PAGE_SIZE so that (ptr + n) % PAGE_SIZE == 0,
> this loop will access two pages (one page containing p == 0 and another
> page containing p == PAGE_SIZE) when this loop should access only one
> page containing p == 0. When checking n bytes, it's range is 0 to n - 1.
oh, so:
p = (unsigned long) ptr;
n = p + n - 1;
--
igor
Igor Stoppa wrote:
> For the case at hand, would it work if there was a non-API call that you
> could use until the API is properly expanded?
Kernel command line switching (i.e. this patch) is fine for my use cases.
SELinux folks might want
-static int security_debug;
+static int security_debug = IS_ENABLED(CONFIG_SECURITY_SELINUX_DISABLE);
so that those who are using SELINUX=disabled in /etc/selinux/config won't
get oops upon boot by default. If "unlock the pool" were available,
SELINUX=enforcing users would be happy. Maybe two modes for rw/ro transition helps.
oneway rw -> ro transition mode: can't be made rw again by calling "unlock the pool" API
twoway rw <-> ro transition mode: can be made rw again by calling "unlock the pool" API
On 06/06/17 17:36, Tetsuo Handa wrote:
> Igor Stoppa wrote:
>> For the case at hand, would it work if there was a non-API call that you
>> could use until the API is properly expanded?
>
> Kernel command line switching (i.e. this patch) is fine for my use cases.
>
> SELinux folks might want
>
> -static int security_debug;
> +static int security_debug = IS_ENABLED(CONFIG_SECURITY_SELINUX_DISABLE);
ok, thanks, I will add this
> so that those who are using SELINUX=disabled in /etc/selinux/config won't
> get oops upon boot by default. If "unlock the pool" were available,
> SELINUX=enforcing users would be happy. Maybe two modes for rw/ro transition helps.
>
> oneway rw -> ro transition mode: can't be made rw again by calling "unlock the pool" API
> twoway rw <-> ro transition mode: can be made rw again by calling "unlock the pool" API
This was in the first cut of the API, but I was told that it would
require further rework, to make it ok for upstream, so we agreed to do
first the lockdown/destroy only part and the the rewrite.
Is there really a valid use case for unloading SE Linux?
Or any other security module.
--
igor
On 6/6/2017 7:51 AM, Igor Stoppa wrote:
> On 06/06/17 17:36, Tetsuo Handa wrote:
>> Igor Stoppa wrote:
>>> For the case at hand, would it work if there was a non-API call that you
>>> could use until the API is properly expanded?
>> Kernel command line switching (i.e. this patch) is fine for my use cases.
>>
>> SELinux folks might want
>>
>> -static int security_debug;
>> +static int security_debug = IS_ENABLED(CONFIG_SECURITY_SELINUX_DISABLE);
> ok, thanks, I will add this
>
>> so that those who are using SELINUX=disabled in /etc/selinux/config won't
>> get oops upon boot by default. If "unlock the pool" were available,
>> SELINUX=enforcing users would be happy. Maybe two modes for rw/ro transition helps.
>>
>> oneway rw -> ro transition mode: can't be made rw again by calling "unlock the pool" API
>> twoway rw <-> ro transition mode: can be made rw again by calling "unlock the pool" API
> This was in the first cut of the API, but I was told that it would
> require further rework, to make it ok for upstream, so we agreed to do
> first the lockdown/destroy only part and the the rewrite.
>
> Is there really a valid use case for unloading SE Linux?
It's used today in the Redhat distros. There is talk of removing it.
You can only unload SELinux before policy is loaded, which is sort of
saying that you have your system misconfigured but can't figure out
how to fix it. You might be able to convince Paul Moore to accelerate
the removal of this feature for this worthy cause.
> Or any other security module.
I suppose that you could argue that if a security module had
been in place for 2 years on a system and had never once denied
anyone access it should be removed. That's a reasonable use case
description, but I doubt you'd encounter it in the real world.
Another possibility is a security module that is used during
container setup and once the system goes into full operation
is no longer needed. Personally, I don't see either of these
cases as compelling. "systemctl restart xyzzyd".
On 06/06/2017 04:34 AM, Igor Stoppa wrote:
> On 06/06/17 09:25, Christoph Hellwig wrote:
>> On Tue, Jun 06, 2017 at 01:44:32PM +0900, Tetsuo Handa wrote:
>
> [..]
>
>>> As far as I know, not all CONFIG_MMU=y architectures provide
>>> set_memory_ro()/set_memory_rw(). You need to provide fallback for
>>> architectures which do not provide set_memory_ro()/set_memory_rw()
>>> or kernels built with CONFIG_MMU=n.
>>
>> I think we'll just need to generalize CONFIG_STRICT_MODULE_RWX and/or
>> ARCH_HAS_STRICT_MODULE_RWX so there is a symbol to key this off.
>
> Would STRICT_KERNEL_RWX work? It's already present.
> If both kernel text and rodata can be protected, so can pmalloc data.
>
> ---
> igor
>
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>
There's already ARCH_HAS_SET_MEMORY for this purpose.
Thanks,
Laura