ima: handle idmapped mounts

IMA does sometimes access the inode's i_uid and compares it against the
rules' fowner. Enable IMA to handle idmapped mounts by passing down the
mount's user namespace. We simply make use of the helpers we introduced
before. If the initial user namespace is passed nothing changes so
non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-27-christian.brauner@ubuntu.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 70b643c41c6b..2e64b9f281cc 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -68,7 +68,8 @@ bool is_ima_appraise_enabled(void)
  *
  * Return 1 to appraise or hash
  */
-int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
+int ima_must_appraise(struct user_namespace *mnt_userns, struct inode *inode,
+		      int mask, enum ima_hooks func)
 {
 	u32 secid;
 
@@ -76,8 +77,8 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
 		return 0;
 
 	security_task_getsecid(current, &secid);
-	return ima_match_policy(inode, current_cred(), secid, func, mask,
-				IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL);
+	return ima_match_policy(mnt_userns, inode, current_cred(), secid, func,
+				mask, IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL);
 }
 
 static int ima_fix_xattr(struct dentry *dentry,
@@ -350,7 +351,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
 
 		rc = is_binary_blacklisted(digest, digestsize);
 		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
-			process_buffer_measurement(NULL, digest, digestsize,
+			process_buffer_measurement(&init_user_ns, NULL, digest, digestsize,
 						   "blacklisted-hash", NONE,
 						   pcr, NULL);
 	}
@@ -501,6 +502,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
 
 /**
  * ima_inode_post_setattr - reflect file metadata changes
+ * @mnt_userns:	user namespace of the mount the inode was found from
  * @dentry: pointer to the affected dentry
  *
  * Changes to a dentry's metadata might result in needing to appraise.
@@ -508,7 +510,8 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
  * This function is called from notify_change(), which expects the caller
  * to lock the inode's i_mutex.
  */
-void ima_inode_post_setattr(struct dentry *dentry)
+void ima_inode_post_setattr(struct user_namespace *mnt_userns,
+			    struct dentry *dentry)
 {
 	struct inode *inode = d_backing_inode(dentry);
 	struct integrity_iint_cache *iint;
@@ -518,7 +521,7 @@ void ima_inode_post_setattr(struct dentry *dentry)
 	    || !(inode->i_opflags & IOP_XATTR))
 		return;
 
-	action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
+	action = ima_must_appraise(mnt_userns, inode, MAY_ACCESS, POST_SETATTR);
 	if (!action)
 		__vfs_removexattr(&init_user_ns, dentry, XATTR_NAME_IMA);
 	iint = integrity_iint_find(inode);