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From:   Chen Jun <chenjun102@huawei.com>
To:     <linux-kernel@vger.kernel.org>, <selinux@vger.kernel.org>
CC:     <casey@schaufler-ca.com>, <stephen.smalley.work@gmail.com>,
        <eparis@parisplace.org>, <rui.xiang@huawei.com>,
        <guohanjun@huawei.com>, <houtao1@huawei.com>
Subject: [RFC PATCH v2] selinux: Fix kmemleak after disabling selinux runtime
Date:   Wed, 28 Oct 2020 02:06:15 +0000
Message-ID: <20201028020615.8789-1-chenjun102@huawei.com>
MIME-Version: 1.0
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Precedence: bulk

From: Chen Jun <c00424029@huawei.com>

Kmemleak will report a problem after using
"echo 1 > /sys/fs/selinux/disable" to disable selinux on runtime.

kmemleak report：
unreferenced object 0xffff901281c208a0 (size 96):
  comm "swapper/0", pid 1, jiffies 4294668265 (age 692.799s)
  hex dump (first 32 bytes):
    00 40 c8 81 12 90 ff ff 03 00 00 00 05 00 00 00  .@..............
    03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<0000000014622ef8>] selinux_sb_alloc_security+0x1b/0xa0
    [<00000000044914e1>] security_sb_alloc+0x1d/0x30
    [<000000009f9d5ffd>] alloc_super+0xa7/0x310
    [<000000003c5f0b5b>] sget_fc+0xca/0x230
    [<00000000367a9996>] vfs_get_super+0x37/0x110
    [<000000001c47e818>] vfs_get_tree+0x20/0xc0
    [<00000000d239b404>] fc_mount+0x9/0x30
    [<00000000708a102f>] vfs_kern_mount.part.36+0x6a/0x80
    [<000000005db542fe>] kern_mount+0x1b/0x30
    [<0000000051919f9f>] init_sel_fs+0x8b/0x119
    [<000000000f328fe0>] do_one_initcall+0x3f/0x1d0
    [<000000008a6ceb81>] kernel_init_freeable+0x1b4/0x1f2
    [<000000003a425dcd>] kernel_init+0x5/0x110
    [<000000004e8d6c9d>] ret_from_fork+0x22/0x30

"echo 1 > /sys/fs/selinux/disable" will delete the hooks.
Any memory alloced by calling HOOKFUNCTION (like call_int_hook(sb_alloc_security, 0, sb))
has no chance to be freed after deleting hooks.

Add a flag to mark a hook not be delete when deleting hooks.

Signed-off-by: Chen Jun <chenjun102@huawei.com>
---
 include/linux/lsm_hooks.h |  6 +++++-
 security/selinux/hooks.c  | 20 ++++++++++----------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index c503f7ab8afb..85de731b0c74 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1554,6 +1554,7 @@ struct security_hook_list {
 	struct hlist_head		*head;
 	union security_list_options	hook;
 	char				*lsm;
+	bool				no_del;
 } __randomize_layout;
 
 /*
@@ -1582,6 +1583,8 @@ struct lsm_blob_sizes {
  */
 #define LSM_HOOK_INIT(HEAD, HOOK) \
 	{ .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
+#define LSM_HOOK_INIT_NO_DEL(HEAD, HOOK) \
+	{ .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK }, .no_del = 1 }
 
 extern struct security_hook_heads security_hook_heads;
 extern char *lsm_names;
@@ -1638,7 +1641,8 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
 	int i;
 
 	for (i = 0; i < count; i++)
-		hlist_del_rcu(&hooks[i].list);
+		if (!hooks[i].no_del)
+			hlist_del_rcu(&hooks[i].list);
 }
 #endif /* CONFIG_SECURITY_SELINUX_DISABLE */
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6b1826fc3658..daff084fd1c7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6974,8 +6974,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(bprm_committing_creds, selinux_bprm_committing_creds),
 	LSM_HOOK_INIT(bprm_committed_creds, selinux_bprm_committed_creds),
 
-	LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security),
-	LSM_HOOK_INIT(sb_free_mnt_opts, selinux_free_mnt_opts),
+	LSM_HOOK_INIT_NO_DEL(sb_free_security, selinux_sb_free_security),
+	LSM_HOOK_INIT_NO_DEL(sb_free_mnt_opts, selinux_free_mnt_opts),
 	LSM_HOOK_INIT(sb_remount, selinux_sb_remount),
 	LSM_HOOK_INIT(sb_kern_mount, selinux_sb_kern_mount),
 	LSM_HOOK_INIT(sb_show_options, selinux_sb_show_options),
@@ -7081,7 +7081,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(ismaclabel, selinux_ismaclabel),
 	LSM_HOOK_INIT(secctx_to_secid, selinux_secctx_to_secid),
-	LSM_HOOK_INIT(release_secctx, selinux_release_secctx),
+	LSM_HOOK_INIT_NO_DEL(release_secctx, selinux_release_secctx),
 	LSM_HOOK_INIT(inode_invalidate_secctx, selinux_inode_invalidate_secctx),
 	LSM_HOOK_INIT(inode_notifysecctx, selinux_inode_notifysecctx),
 	LSM_HOOK_INIT(inode_setsecctx, selinux_inode_setsecctx),
@@ -7107,7 +7107,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(socket_getpeersec_stream,
 			selinux_socket_getpeersec_stream),
 	LSM_HOOK_INIT(socket_getpeersec_dgram, selinux_socket_getpeersec_dgram),
-	LSM_HOOK_INIT(sk_free_security, selinux_sk_free_security),
+	LSM_HOOK_INIT_NO_DEL(sk_free_security, selinux_sk_free_security),
 	LSM_HOOK_INIT(sk_clone_security, selinux_sk_clone_security),
 	LSM_HOOK_INIT(sk_getsecid, selinux_sk_getsecid),
 	LSM_HOOK_INIT(sock_graft, selinux_sock_graft),
@@ -7121,7 +7121,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(secmark_refcount_inc, selinux_secmark_refcount_inc),
 	LSM_HOOK_INIT(secmark_refcount_dec, selinux_secmark_refcount_dec),
 	LSM_HOOK_INIT(req_classify_flow, selinux_req_classify_flow),
-	LSM_HOOK_INIT(tun_dev_free_security, selinux_tun_dev_free_security),
+	LSM_HOOK_INIT_NO_DEL(tun_dev_free_security, selinux_tun_dev_free_security),
 	LSM_HOOK_INIT(tun_dev_create, selinux_tun_dev_create),
 	LSM_HOOK_INIT(tun_dev_attach_queue, selinux_tun_dev_attach_queue),
 	LSM_HOOK_INIT(tun_dev_attach, selinux_tun_dev_attach),
@@ -7130,7 +7130,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(ib_pkey_access, selinux_ib_pkey_access),
 	LSM_HOOK_INIT(ib_endport_manage_subnet,
 		      selinux_ib_endport_manage_subnet),
-	LSM_HOOK_INIT(ib_free_security, selinux_ib_free_security),
+	LSM_HOOK_INIT_NO_DEL(ib_free_security, selinux_ib_free_security),
 #endif
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
 	LSM_HOOK_INIT(xfrm_policy_free_security, selinux_xfrm_policy_free),
@@ -7144,7 +7144,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 #endif
 
 #ifdef CONFIG_KEYS
-	LSM_HOOK_INIT(key_free, selinux_key_free),
+	LSM_HOOK_INIT_NO_DEL(key_free, selinux_key_free),
 	LSM_HOOK_INIT(key_permission, selinux_key_permission),
 	LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
 #ifdef CONFIG_KEY_NOTIFICATIONS
@@ -7162,13 +7162,13 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(bpf, selinux_bpf),
 	LSM_HOOK_INIT(bpf_map, selinux_bpf_map),
 	LSM_HOOK_INIT(bpf_prog, selinux_bpf_prog),
-	LSM_HOOK_INIT(bpf_map_free_security, selinux_bpf_map_free),
-	LSM_HOOK_INIT(bpf_prog_free_security, selinux_bpf_prog_free),
+	LSM_HOOK_INIT_NO_DEL(bpf_map_free_security, selinux_bpf_map_free),
+	LSM_HOOK_INIT_NO_DEL(bpf_prog_free_security, selinux_bpf_prog_free),
 #endif
 
 #ifdef CONFIG_PERF_EVENTS
 	LSM_HOOK_INIT(perf_event_open, selinux_perf_event_open),
-	LSM_HOOK_INIT(perf_event_free, selinux_perf_event_free),
+	LSM_HOOK_INIT_NO_DEL(perf_event_free, selinux_perf_event_free),
 	LSM_HOOK_INIT(perf_event_read, selinux_perf_event_read),
 	LSM_HOOK_INIT(perf_event_write, selinux_perf_event_write),
 #endif
-- 
2.25.0