landlock: fix splats from iput() after it started calling might_sleep()

At this point it is guaranteed this is not the last reference.

However, a recent addition of might_sleep() at top of iput() started
generating false-positives as it was executing for all values.

Remedy the problem by using the newly introduced iput_not_last().

Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68d32659.a70a0220.4f78.0012.GAE@google.com/
Fixes: 2ef435a872ab ("fs: add might_sleep() annotation to iput() and more")
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20251105212025.807549-2-mjguzik@gmail.com
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 0bade2c5aa1d007e6e13951aba19ae01d21a9baf..d9c12b993fa7dd7e27d4a6df509e69b29367fa62 100644 (file)
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1335,11 +1335,10 @@ static void hook_sb_delete(struct super_block *const sb)
                         * At this point, we own the ihold() reference that was
                         * originally set up by get_inode_object() and the
                         * __iget() reference that we just set in this loop
-                        * walk.  Therefore the following call to iput() will
-                        * not sleep nor drop the inode because there is now at
-                        * least two references to it.
+                        * walk.  Therefore there are at least two references
+                        * on the inode.
                         */
-                       iput(inode);
+                       iput_not_last(inode);
                } else {
                        spin_unlock(&object->lock);
                        rcu_read_unlock();