kernfs: Avoid namespace dereference in d_revalidate()

Commit 1fe989e1c42a ("kernfs: use namespace id instead of pointer for
hashing and comparison") changed dentry revalidation to compare namespace
IDs along with the comparisons that determine visible directory ordering.

Dereferencing a namespace tag that kernfs_rename_ns() can replace is not
suitable once dentry revalidation stops taking kernfs_rwsem. Use pointer
equality for this non-user-visible equality check instead. Namespace IDs
uniquely identify namespace objects, so pointer and ID equality cannot
disagree for valid tags. Hashing and directory ordering continue to use
IDs.

kn->ns becomes a lockless read in the next commit, so mark both sides of
it now. The read is in kernfs_dop_revalidate(); the stores that can run
while the node is visible are the two in kernfs_rename_ns(). The remaining
stores, in kernfs_create_dir_ns(), kernfs_create_empty_dir() and
kernfs_create_link(), all precede kernfs_add_one() and need no marking.

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Link: https://patch.msgid.link/20260821050507.2161607-4-shakeel.butt@linux.dev
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions