A secure anonymous file is one we hooked up to its own inode (as
opposed to the shared inode we use for non-secure anonymous files). A
new selinux hook gives security modules a chance to initialize, label,
and veto the creation of these secure anonymous files. Security
modules had limit ability to interact with non-secure anonymous files
due to all of these files sharing a single inode.
Signed-off-by: Daniel Colascione <[email protected]>
---
fs/anon_inodes.c | 45 ++++++++++++++++++++++++++++++---------
include/linux/lsm_hooks.h | 8 +++++++
include/linux/security.h | 2 ++
security/security.c | 8 +++++++
4 files changed, 53 insertions(+), 10 deletions(-)
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index caa36019afca..d68d76523ad3 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -55,6 +55,23 @@ static struct file_system_type anon_inode_fs_type = {
.kill_sb = kill_anon_super,
};
+struct inode *anon_inode_make_secure_inode(const char *name,
+ const struct file_operations *fops)
+{
+ struct inode *inode;
+ int error;
+ inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
+ if (IS_ERR(inode))
+ return ERR_PTR(PTR_ERR(inode));
+ inode->i_flags &= ~S_PRIVATE;
+ error = security_inode_init_security_anon(inode, name, fops);
+ if (error) {
+ iput(inode);
+ return ERR_PTR(error);
+ }
+ return inode;
+}
+
/**
* anon_inode_getfile2 - creates a new file instance by hooking it up to
* an anonymous inode, and a dentry that describe
@@ -72,7 +89,9 @@ static struct file_system_type anon_inode_fs_type = {
* hence saving memory and avoiding code duplication for the file/inode/dentry
* setup. Returns the newly created file* or an error pointer.
*
- * anon_inode_flags must be zero.
+ * If anon_inode_flags contains ANON_INODE_SECURE, create a new inode
+ * and enable security checks for it. Otherwise, attach a new file to
+ * a singleton placeholder inode with security checks disabled.
*/
struct file *anon_inode_getfile2(const char *name,
const struct file_operations *fops,
@@ -81,17 +100,23 @@ struct file *anon_inode_getfile2(const char *name,
struct inode *inode;
struct file *file;
- if (anon_inode_flags)
+ if (anon_inode_flags & ~ANON_INODE_SECURE)
return ERR_PTR(-EINVAL);
- inode = anon_inode_inode;
- if (IS_ERR(inode))
- return ERR_PTR(-ENODEV);
- /*
- * We know the anon_inode inode count is always
- * greater than zero, so ihold() is safe.
- */
- ihold(inode);
+ if (anon_inode_flags & ANON_INODE_SECURE) {
+ inode = anon_inode_make_secure_inode(name, fops);
+ if (IS_ERR(inode))
+ return ERR_PTR(PTR_ERR(inode));
+ } else {
+ inode = anon_inode_inode;
+ if (IS_ERR(inode))
+ return ERR_PTR(-ENODEV);
+ /*
+ * We know the anon_inode inode count is always
+ * greater than zero, so ihold() is safe.
+ */
+ ihold(inode);
+ }
if (fops->owner && !try_module_get(fops->owner)) {
file = ERR_PTR(-ENOENT);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 20d8cf194fb7..ba208ce5711d 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -215,6 +215,10 @@
* Returns 0 if @name and @value have been successfully set,
* -EOPNOTSUPP if no security attribute is needed, or
* -ENOMEM on memory allocation failure.
+ * @inode_init_security_anon:
+ * Set up a secure anonymous inode.
+ * Returns 0 on success. Returns -EPERM if the security module denies
+ * the creation of this inode.
* @inode_create:
* Check permission to create a regular file.
* @dir contains inode structure of the parent of the new file.
@@ -1552,6 +1556,9 @@ union security_list_options {
const struct qstr *qstr,
const char **name, void **value,
size_t *len);
+ int (*inode_init_security_anon)(struct inode *inode,
+ const char *name,
+ const struct file_operations *fops);
int (*inode_create)(struct inode *dir, struct dentry *dentry,
umode_t mode);
int (*inode_link)(struct dentry *old_dentry, struct inode *dir,
@@ -1884,6 +1891,7 @@ struct security_hook_heads {
struct hlist_head inode_alloc_security;
struct hlist_head inode_free_security;
struct hlist_head inode_init_security;
+ struct hlist_head inode_init_security_anon;
struct hlist_head inode_create;
struct hlist_head inode_link;
struct hlist_head inode_unlink;
diff --git a/include/linux/security.h b/include/linux/security.h
index 64b19f050343..8625b647dd0b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -320,6 +320,8 @@ void security_inode_free(struct inode *inode);
int security_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr,
initxattrs initxattrs, void *fs_data);
+int security_inode_init_security_anon(struct inode *inode, const char *name,
+ const struct file_operations *fops);
int security_old_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr, const char **name,
void **value, size_t *len);
diff --git a/security/security.c b/security/security.c
index 565bc9b67276..78dc6096b30f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1033,6 +1033,14 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
}
EXPORT_SYMBOL(security_inode_init_security);
+int
+security_inode_init_security_anon(struct inode *inode,
+ const char *name,
+ const struct file_operations *fops)
+{
+ return call_int_hook(inode_init_security_anon, 0, inode, name, fops);
+}
+
int security_old_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr, const char **name,
void **value, size_t *len)
--
2.25.0.225.g125e21ebc7-goog
On 2/11/20 5:55 PM, Daniel Colascione wrote:
> A secure anonymous file is one we hooked up to its own inode (as
> opposed to the shared inode we use for non-secure anonymous files). A
> new selinux hook gives security modules a chance to initialize, label,
> and veto the creation of these secure anonymous files. Security
> modules had limit ability to interact with non-secure anonymous files
> due to all of these files sharing a single inode.
>
> Signed-off-by: Daniel Colascione <[email protected]>
(please add linux-fsdevel, viro, linux-security-module,
[email protected], [email protected] to cc on future versions of this
patch since it is a VFS and a LSM change)
> --- > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 20d8cf194fb7..ba208ce5711d 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -215,6 +215,10 @@
> * Returns 0 if @name and @value have been successfully set,
> * -EOPNOTSUPP if no security attribute is needed, or
> * -ENOMEM on memory allocation failure.
> + * @inode_init_security_anon:
> + * Set up a secure anonymous inode.
> + * Returns 0 on success. Returns -EPERM if the security module denies
> + * the creation of this inode.
Please document the parameters for the hook as well.
Hi Daniel,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on pcmoore-selinux/next]
[also build test ERROR on security/next-testing linux/master linus/master v5.6-rc1 next-20200214]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Daniel-Colascione/Harden-userfaultfd/20200215-034039
base: https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git next
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.5.0-4) 7.5.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <[email protected]>
All errors (new ones prefixed by >>):
fs/anon_inodes.c: In function 'anon_inode_make_secure_inode':
>> fs/anon_inodes.c:67:10: error: implicit declaration of function 'security_inode_init_security_anon'; did you mean 'security_inode_init_security'? [-Werror=implicit-function-declaration]
error = security_inode_init_security_anon(inode, name, fops);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
security_inode_init_security
cc1: some warnings being treated as errors
vim +67 fs/anon_inodes.c
57
58 struct inode *anon_inode_make_secure_inode(const char *name,
59 const struct file_operations *fops)
60 {
61 struct inode *inode;
62 int error;
63 inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
64 if (IS_ERR(inode))
65 return ERR_PTR(PTR_ERR(inode));
66 inode->i_flags &= ~S_PRIVATE;
> 67 error = security_inode_init_security_anon(inode, name, fops);
68 if (error) {
69 iput(inode);
70 return ERR_PTR(error);
71 }
72 return inode;
73 }
74
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]