[PATCH v5 27/42] notify: handle idmapped mounts

[Christian Brauner <christian.brauner@ubuntu.com>]

Enable notify implementations to handle idmapped mounts by passing down
the mount's user namespace. If the initial user namespace is passed
nothing changes so non-idmapped mounts will see identical behavior as
before.

Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
patch introduced

/* v3 */
unchanged

/* v4 */
unchanged

/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837
---
 fs/notify/fanotify/fanotify_user.c | 2 +-
 fs/notify/inotify/inotify_user.c   | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 4ca13fb33c7c..c60b8cc1f94d 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -702,7 +702,7 @@ static int fanotify_find_path(int dfd, const char __user *filename,
 	}
 
 	/* you can only watch an inode if you have read permissions on it */
-	ret = inode_permission(&init_user_ns, path->dentry->d_inode, MAY_READ);
+	ret = inode_permission(mnt_user_ns(path->mnt), path->dentry->d_inode, MAY_READ);
 	if (ret) {
 		path_put(path);
 		goto out;
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 18e7024207a9..cecff22549d7 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -31,6 +31,7 @@
 #include <linux/wait.h>
 #include <linux/memcontrol.h>
 #include <linux/security.h>
+#include <linux/mount.h>
 
 #include "inotify.h"
 #include "../fdinfo.h"
@@ -352,7 +353,7 @@ static int inotify_find_inode(const char __user *dirname, struct path *path,
 	if (error)
 		return error;
 	/* you can only watch an inode if you have read permissions on it */
-	error = inode_permission(&init_user_ns, path->dentry->d_inode, MAY_READ);
+	error = inode_permission(mnt_user_ns(path->mnt), path->dentry->d_inode, MAY_READ);
 	if (error) {
 		path_put(path);
 		return error;
-- 
2.30.0