Hello Christoph, stable,
I recently saw a crash caused by the kintegrityd workqueue that could only be reproduced on older kernels. A null pointer dereference in function bio_integrity_verify_fn.
The fix in Linus's tree for this: 3df49967f6f1 ("block: flush the integrity workqueue in blk_integrity_unregister") was first merged in v5.15.
The fix has been backported to v5.10 LTS branch in: 1ef68b84bc11 ("block: flush the integrity workqueue in blk_integrity_unregister")
The fix doesn't have a fixes tag, but from inspecting the code, I don't understand why this was only backported to v5.10, AFAICT it should at least have been backported to v5.4, v4.19 and v4.14 LTS as well.
Original series: https://lore.kernel.org/all/20210914070657.87677-3-hch@lst.de/
The blk_flush_integrity() call that actually fixes the crash should be trivial to backport/add before clearing the flag and doing the memset.
Kind regards, Niklas