ksmbd: fix lookup on idmapped mounts
It's great that the new in-kernel ksmbd server will support idmapped
mounts out of the box! However, lookup is currently broken. Lookup
helpers such as lookup_one_len() call inode_permission() internally to
ensure that the caller is privileged over the inode of the base dentry
they are trying to lookup under. So the permission checking here is
currently wrong.
Linux v5.15 will gain a new lookup helper lookup_one() that does take
idmappings into account. I've added it as part of my patch series to
make btrfs support idmapped mounts. The new helper is in linux-next as
part of David's (Sterba) btrfs for-next branch as commit
c972214c133b ("namei: add mapping aware lookup helper").
I've said it before during one of my first reviews: I would very much
recommend adding fstests to [1]. It already seems to have very
rudimentary cifs support. There is a completely generic idmapped mount
testsuite that supports idmapped mounts.
[1]: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/
Cc: Steve French <stfrench@microsoft.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
I merged David's for-next tree into cifsd-next to test this. I did only
compile test this. If someone gives me a clear set of instructions how
to test ksmbd on my local machine I can at least try to cut some time
out of my week to do more reviews. (I'd especially like to see acl
behavior with ksmbd.)
One more thing, the tree for ksmbd was very hard to find. I had to do a
lot archeology to end up at:
git://git.samba.org/ksmbd.git
Would be appreciated if this tree could be reflected in MAINTAINERS or
somewhere else. The github repos with the broken out patches/module
aren't really that helpful.
Thanks!
Christian
3 files changed
