[PATCH 5/9] LSM: Introduce inode_post_setattr hook

Kees Cook
2022-10-13T22:37:39Z

IMA and EVM need to hook after setattr finishes. Introduce this hook and
move IMA and EVM's open-coded stacking to use it.

Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Jonathan McDowell <noodles@fb.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-integrity@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/attr.c | 3 +--
include/linux/evm.h | 6 ------
include/linux/ima.h | 9 ---------
include/linux/lsm_hook_defs.h | 3 +++
security/integrity/evm/evm_main.c | 10 +++++++++-
security/integrity/ima/ima.h | 2 ++
security/integrity/ima/ima_appraise.c | 2 +-
security/integrity/ima/ima_main.c | 1 +
security/security.c | 8 ++++++++
9 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/fs/attr.c b/fs/attr.c
index 1552a5f23d6b..e5731057426b 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -423,8 +423,7 @@ int notify_change(struct user_namespace *mnt_userns, struct dentry *dentry,

if (!error) {
fsnotify_change(dentry, ia_valid);
- ima_inode_post_setattr(mnt_userns, dentry);
- evm_inode_post_setattr(dentry, ia_valid);
+ security_inode_post_setattr(mnt_userns, dentry, ia_valid);
}

return error;
diff --git a/include/linux/evm.h b/include/linux/evm.h
index aa63e0b3c0a2..53f402bfb9f1 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -23,7 +23,6 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
struct integrity_iint_cache *iint);
extern int evm_inode_setattr(struct user_namespace *mnt_userns,
struct dentry *dentry, struct iattr *attr);
-extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid);
extern int evm_inode_setxattr(struct user_namespace *mnt_userns,
struct dentry *dentry, const char *name,
const void *value, size_t size);
@@ -75,11 +74,6 @@ static inline int evm_inode_setattr(struct user_namespace *mnt_userns,
return 0;
}

-static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
-{
- return;
-}
-
static inline int evm_inode_setxattr(struct user_namespace *mnt_userns,
struct dentry *dentry, const char *name,
const void *value, size_t size)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 9f18df366064..70180b9bd974 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -127,20 +127,11 @@ static inline void ima_post_key_create_or_update(struct key *keyring,

#ifdef CONFIG_IMA_APPRAISE
extern bool is_ima_appraise_enabled(void);
-extern void ima_inode_post_setattr(struct user_namespace *mnt_userns,
- struct dentry *dentry);
#else
static inline bool is_ima_appraise_enabled(void)
{
return 0;
}
-
-static inline void ima_inode_post_setattr(struct user_namespace *mnt_userns,
- struct dentry *dentry)
-{
- return;
-}
-
#endif /* CONFIG_IMA_APPRAISE */

#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 806448173033..0b01473eee8a 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -135,6 +135,9 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode,
bool rcu)
LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask)
LSM_HOOK(int, 0, inode_setattr, struct dentry *dentry, struct iattr *attr)
+LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr,
+ struct user_namespace *mnt_userns, struct dentry *dentry,
+ unsigned int ia_valid)
LSM_HOOK(int, 0, inode_getattr, const struct path *path)
LSM_HOOK(int, 0, inode_setxattr, struct user_namespace *mnt_userns,
struct dentry *dentry, const char *name, const void *value,
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 1ef965089417..aca689dc0576 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -817,7 +817,9 @@ int evm_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
* This function is called from notify_change(), which expects the caller
* to lock the inode's i_mutex.
*/
-void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
+static void evm_inode_post_setattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry,
+ unsigned int ia_valid)
{
if (!evm_revalidate_status(NULL))
return;
@@ -905,6 +907,12 @@ static int __init init_evm(void)

late_initcall(init_evm);

+static struct security_hook_list evm_hooks[] __lsm_ro_after_init = {
+ LSM_HOOK_INIT(inode_post_setattr, evm_inode_post_setattr),
+};
+
void __init integrity_lsm_evm_init(void)
{
+ pr_info("Integrity LSM enabling EVM\n");
+ integrity_add_lsm_hooks(evm_hooks, ARRAY_SIZE(evm_hooks));
}
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 15a369df4c00..5c95ea6e6c94 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -176,6 +176,8 @@ int ima_inode_setxattr(struct user_namespace *mnt_userns,
int flags);
int ima_inode_removexattr(struct user_namespace *mnt_userns,
struct dentry *dentry, const char *xattr_name);
+void ima_inode_post_setattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, unsigned int ia_valid);
#endif

/*
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index ddd9df6b7dac..ccd54b50fe48 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -631,7 +631,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
* to lock the inode's i_mutex.
*/
void ima_inode_post_setattr(struct user_namespace *mnt_userns,
- struct dentry *dentry)
+ struct dentry *dentry, unsigned int ia_valid)
{
struct inode *inode = d_backing_inode(dentry);
struct integrity_iint_cache *iint;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 94379ba40b58..ffebd3236f24 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -1093,6 +1093,7 @@ static struct security_hook_list ima_hooks[] __lsm_ro_after_init = {
#ifdef CONFIG_IMA_APPRAISE
LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr),
LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr),
+ LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr),
#endif
};

diff --git a/security/security.c b/security/security.c
index ca731132a0e9..af42264ad3e2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1333,6 +1333,14 @@ int security_inode_setattr(struct user_namespace *mnt_userns,
}
EXPORT_SYMBOL_GPL(security_inode_setattr);

+void security_inode_post_setattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, unsigned int ia_valid)
+{
+ if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+ return;
+ call_void_hook(inode_post_setattr, mnt_userns, dentry, ia_valid);
+}
+
int security_inode_getattr(const struct path *path)
{
if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
--
2.34.1