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[15/24] btrfs/ioctl: check whether fs{g,u}id are mapped during subvolume creation

Message ID 20210713111344.1149376-16-brauner@kernel.org (mailing list archive)
State New, archived
Headers show
Series btrfs: support idmapped mounts | expand

Commit Message

Christian Brauner July 13, 2021, 11:13 a.m. UTC 
From: Christian Brauner <christian.brauner@ubuntu.com>

When a new subvolume is created btrfs currently doesn't check whether the
fs{g,u}id of the caller actually have a mapping in the user namespace attached
to the filesystem. The vfs always checks this to make sure that the caller's
fs{g,u}id can be represented on-disk. This is most relevant for filesystems
that can be mounted inside user namespaces but it is in general a good
hardening measure to prevent unrepresentable {g,u}ids from being written to
disk.
Since we want to support idmapped mounts for btrfs ioctls to create subvolumes
in follow-up patches this becomes important since we want to make sure the
fs{g,u}id of the caller as mapped according to the idmapped mount can be
represented on-disk. Simply add the missing fsuidgid_has_mapping() line from
the vfs may_create() version to btrfs_may_create().

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 fs/btrfs/ioctl.c | 2 ++
 1 file changed, 2 insertions(+)
diff mbox series

Patch

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8ec67e52fde3..f332de258058 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -870,6 +870,8 @@  static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
 		return -EEXIST;
 	if (IS_DEADDIR(dir))
 		return -ENOENT;
+	if (!fsuidgid_has_mapping(dir->i_sb, &init_user_ns))
+		return -EOVERFLOW;
 	return inode_permission(&init_user_ns, dir, MAY_WRITE | MAY_EXEC);
 }