fs: port inode_owner_or_capable() to mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 637f8bee7132..48dd44251dda 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1197,7 +1197,7 @@ int may_linkat(struct mnt_idmap *idmap, const struct path *link)
 	 * otherwise, it must be a safe source.
 	 */
 	if (safe_hardlink_source(idmap, inode) ||
-	    inode_owner_or_capable(mnt_userns, inode))
+	    inode_owner_or_capable(idmap, inode))
 		return 0;
 
 	audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
@@ -3158,7 +3158,6 @@ bool may_open_dev(const struct path *path)
 static int may_open(struct mnt_idmap *idmap, const struct path *path,
 		    int acc_mode, int flag)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct dentry *dentry = path->dentry;
 	struct inode *inode = dentry->d_inode;
 	int error;
@@ -3207,7 +3206,7 @@ static int may_open(struct mnt_idmap *idmap, const struct path *path,
 	}
 
 	/* O_NOATIME can only be set by the owner or superuser */
-	if (flag & O_NOATIME && !inode_owner_or_capable(mnt_userns, inode))
+	if (flag & O_NOATIME && !inode_owner_or_capable(idmap, inode))
 		return -EPERM;
 
 	return 0;