Re: [PATCH 0/4] vfs: if RESOLVE_NO_XDEV passed to openat2, don't *trigger* automounts

[Christian Brauner <brauner@kernel.org>]

On Sun, Aug 17, 2025 at 05:15:09PM +0000, Askar Safin wrote:
> openat2 had a bug: if we pass RESOLVE_NO_XDEV, then openat2
> doesn't traverse through automounts, but may still trigger them.
> See this link for full bug report with reproducer:
> https://lore.kernel.org/linux-fsdevel/20250817075252.4137628-1-safinaskar@zohomail.com/
> 
> This patchset fixes the bug.

Thanks, this looks all sane. Once you've addressed all comments I'll get
this into -next.

> RESOLVE_NO_XDEV logic hopefully becomes more clear:
> now we immediately fail when we cross mountpoints.
> 
> I think this patchset should get to -fixes and stable trees.
> 
> I split everything to very small commits to make
> everything as bisectable as possible.

Thanks! But as said ealier in the thread folding the first three
preparatory patches is fine.

> 
> Minimal testing was performed. I tested that my original
> reproducer doesn't reproduce anymore. And I did boot-test
> with localmodconfig in qemu
> 
> I'm not very attached to this patchset. I. e. I will not be offended
> if someone else will submit different fix for this bug.
> 
> Askar Safin (4):
>   vfs: fs/namei.c: move cross-device check to traverse_mounts
>   vfs: fs/namei.c: remove LOOKUP_NO_XDEV check from handle_mounts
>   vfs: fs/namei.c: move cross-device check to __traverse_mounts
>   vfs: fs/namei.c: if RESOLVE_NO_XDEV passed to openat2, don't *trigger*
>     automounts
> 
>  fs/namei.c | 29 +++++++++++++++++++++++------
>  1 file changed, 23 insertions(+), 6 deletions(-)
> 
> -- 
> 2.47.2
>