In the Linux kernel, the following vulnerability has been resolved:

gfs2: fix quota init duplicate scan

gfs2 quota init() checks for duplicate quota change IDs while holding qd lock and the quota hash bucket bitlock. That path used gfs2 qd search bucket(), which takes a lockref reference via lockref get not dead().

On PREEMPT RT this may sleep, which is not allowed under the bucket bitlock, triggering "sleeping function called from invalid context".

Use a no-ref bucket lookup in this path, then continue duplicate handling without taking a lockref there.

Refactor gfs2 qd search bucket() to build on top of the no-ref helper so lookup traversal stays in one place.

This patch fixes a bug reported by syzbot.