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, 6 insertions, 7 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7c6bb1ff41b3..6affe071bdfd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1248,7 +1248,6 @@ static noinline int __btrfs_ioctl_snap_create(struct file *file,
 {
 	int namelen;
 	int ret = 0;
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	if (!S_ISDIR(file_inode(file)->i_mode))
 		return -ENOTDIR;
@@ -1285,7 +1284,7 @@ static noinline int __btrfs_ioctl_snap_create(struct file *file,
 			btrfs_info(BTRFS_I(file_inode(file))->root->fs_info,
 				   "Snapshot src from another FS");
 			ret = -EXDEV;
-		} else if (!inode_owner_or_capable(mnt_userns, src_inode)) {
+		} else if (!inode_owner_or_capable(idmap, src_inode)) {
 			/*
 			 * Subvolume creation is not restricted, but snapshots
 			 * are limited to own subvolumes only
@@ -1424,7 +1423,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
 	u64 flags;
 	int ret = 0;
 
-	if (!inode_owner_or_capable(file_mnt_user_ns(file), inode))
+	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
 		return -EPERM;
 
 	ret = mnt_want_write_file(file);
@@ -3909,7 +3908,7 @@ static long btrfs_ioctl_quota_rescan_wait(struct btrfs_fs_info *fs_info,
 }
 
 static long _btrfs_ioctl_set_received_subvol(struct file *file,
-					    struct user_namespace *mnt_userns,
+					    struct mnt_idmap *idmap,
 					    struct btrfs_ioctl_received_subvol_args *sa)
 {
 	struct inode *inode = file_inode(file);
@@ -3921,7 +3920,7 @@ static long _btrfs_ioctl_set_received_subvol(struct file *file,
 	int ret = 0;
 	int received_uuid_changed;
 
-	if (!inode_owner_or_capable(mnt_userns, inode))
+	if (!inode_owner_or_capable(idmap, inode))
 		return -EPERM;
 
 	ret = mnt_want_write_file(file);
@@ -4026,7 +4025,7 @@ static long btrfs_ioctl_set_received_subvol_32(struct file *file,
 	args64->rtime.nsec = args32->rtime.nsec;
 	args64->flags = args32->flags;
 
-	ret = _btrfs_ioctl_set_received_subvol(file, file_mnt_user_ns(file), args64);
+	ret = _btrfs_ioctl_set_received_subvol(file, file_mnt_idmap(file), args64);
 	if (ret)
 		goto out;
 
@@ -4060,7 +4059,7 @@ static long btrfs_ioctl_set_received_subvol(struct file *file,
 	if (IS_ERR(sa))
 		return PTR_ERR(sa);
 
-	ret = _btrfs_ioctl_set_received_subvol(file, file_mnt_user_ns(file), sa);
+	ret = _btrfs_ioctl_set_received_subvol(file, file_mnt_idmap(file), sa);
 
 	if (ret)
 		goto out;