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, 24 insertions, 13 deletions

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index f87cb29329e9..cb1c56eccd6d 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -218,8 +218,8 @@ static int process_measurement(struct file *file, const struct cred *cred,
 	 * bitmask based on the appraise/audit/measurement policy.
 	 * Included is the appraise submask.
 	 */
-	action = ima_get_action(inode, cred, secid, mask, func, &pcr,
-				&template_desc, NULL);
+	action = ima_get_action(file_mnt_user_ns(file), inode, cred, secid,
+				mask, func, &pcr, &template_desc, NULL);
 	violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
 			   (ima_policy_flag & IMA_MEASURE));
 	if (!action && !violation_check)
@@ -431,8 +431,9 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
 
 	security_task_getsecid(current, &secid);
 	inode = file_inode(vma->vm_file);
-	action = ima_get_action(inode, current_cred(), secid, MAY_EXEC,
-				MMAP_CHECK, &pcr, &template, 0);
+	action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
+				current_cred(), secid, MAY_EXEC, MMAP_CHECK,
+				&pcr, &template, 0);
 
 	/* Is the mmap'ed file in policy? */
 	if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
@@ -592,18 +593,21 @@ EXPORT_SYMBOL_GPL(ima_inode_hash);
 
 /**
  * ima_post_create_tmpfile - mark newly created tmpfile as new
+ * @mnt_userns:	user namespace of the mount the inode was found from
  * @file : newly created tmpfile
  *
  * No measuring, appraising or auditing of newly created tmpfiles is needed.
  * Skip calling process_measurement(), but indicate which newly, created
  * tmpfiles are in policy.
  */
-void ima_post_create_tmpfile(struct inode *inode)
+void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
+			     struct inode *inode)
 {
 	struct integrity_iint_cache *iint;
 	int must_appraise;
 
-	must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
+	must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
+					  FILE_CHECK);
 	if (!must_appraise)
 		return;
 
@@ -619,18 +623,21 @@ void ima_post_create_tmpfile(struct inode *inode)
 
 /**
  * ima_post_path_mknod - mark as a new inode
+ * @mnt_userns:	user namespace of the mount the inode was found from
  * @dentry: newly created dentry
  *
  * Mark files created via the mknodat syscall as new, so that the
  * file data can be written later.
  */
-void ima_post_path_mknod(struct dentry *dentry)
+void ima_post_path_mknod(struct user_namespace *mnt_userns,
+			 struct dentry *dentry)
 {
 	struct integrity_iint_cache *iint;
 	struct inode *inode = dentry->d_inode;
 	int must_appraise;
 
-	must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
+	must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
+					  FILE_CHECK);
 	if (!must_appraise)
 		return;
 
@@ -810,6 +817,7 @@ int ima_post_load_data(char *buf, loff_t size,
 
 /*
  * process_buffer_measurement - Measure the buffer to ima log.
+ * @mnt_userns:	user namespace of the mount the inode was found from
  * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
  * @buf: pointer to the buffer that needs to be added to the log.
  * @size: size of buffer(in bytes).
@@ -820,7 +828,8 @@ int ima_post_load_data(char *buf, loff_t size,
  *
  * Based on policy, the buffer is measured into the ima log.
  */
-void process_buffer_measurement(struct inode *inode, const void *buf, int size,
+void process_buffer_measurement(struct user_namespace *mnt_userns,
+				struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
 				int pcr, const char *keyring)
 {
@@ -860,8 +869,9 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 	 */
 	if (func) {
 		security_task_getsecid(current, &secid);
-		action = ima_get_action(inode, current_cred(), secid, 0, func,
-					&pcr, &template, keyring);
+		action = ima_get_action(mnt_userns, inode, current_cred(),
+					secid, 0, func, &pcr, &template,
+					keyring);
 		if (!(action & IMA_MEASURE))
 			return;
 	}
@@ -919,8 +929,9 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 	if (!f.file)
 		return;
 
-	process_buffer_measurement(file_inode(f.file), buf, size,
-				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
+	process_buffer_measurement(file_mnt_user_ns(f.file), file_inode(f.file),
+				   buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
+				   NULL);
 	fdput(f);
 }