[PATCH 5.10 087/103] block: flush the integrity workqueue in blk_integrity_unregister

[Greg Kroah-Hartman]

From: Lihong Kou <koulihong@xxxxxxxxxx>

[ Upstream commit 3df49967f6f1d2121b0c27c381ca1c8386b1dab9 ]

When the integrity profile is unregistered there can still be integrity
reads queued up which could see a NULL verify_fn as shown by the race
window below:

CPU0                                    CPU1
  process_one_work                      nvme_validate_ns
    bio_integrity_verify_fn                nvme_update_ns_info
	                                     nvme_update_disk_info
	                                       blk_integrity_unregister
                                               ---set queue->integrity as 0
	bio_integrity_process
	--access bi->profile->verify_fn(bi is a pointer of queue->integity)

Before calling blk_integrity_unregister in nvme_update_disk_info, we must
make sure that there is no work item in the kintegrityd_wq. Just call
blk_flush_integrity to flush the work queue so the bug can be resolved.

Signed-off-by: Lihong Kou <koulihong@xxxxxxxxxx>
[hch: split up and shortened the changelog]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210914070657.87677-3-hch@xxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 block/blk-integrity.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index e9f943de377a..9e83159f5a52 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -430,6 +430,9 @@ void blk_integrity_unregister(struct gendisk *disk)
 
 	if (!bi->profile)
 		return;
+
+	/* ensure all bios are off the integrity workqueue */
+	blk_flush_integrity();
 	blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, disk->queue);
 	memset(bi, 0, sizeof(*bi));
 }
-- 
2.33.0