openat2: don't trigger automounts with RESOLVE_NO_XDEV

openat2 had a bug: if we pass RESOLVE_NO_XDEV, then openat2
doesn't traverse through automounts, but may still trigger them.
(See the link for full bug report with reproducer.)

This commit fixes this bug.

Link: https://lore.kernel.org/linux-fsdevel/20250817075252.4137628-1-safinaskar@zohomail.com/


Fixes: fddb5d43 ("open: introduce openat2(2) syscall")
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Cc: stable@vger.kernel.org
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250825181233.2464822-5-safinaskar@zohomail.com


Signed-off-by: Christian Brauner <brauner@kernel.org>