From 5eabbf4eed4a10bc5a0b28436ed79e87d25b008b Mon Sep 17 00:00:00 2001

From: Jan Kara <jack@suse.cz>

Date: Wed, 5 Jan 2022 14:21:04 +0100

Subject: [PATCH 4/9] bfq: Update cgroup information before merging bio

References: bsc#1197926

Patch-mainline: submitted, in linux-block tree

When the process is migrated to a different cgroup (or in case of

writeback just starts submitting bios associated with a different

cgroup) bfq_merge_bio() can operate with stale cgroup information in

bic. Thus the bio can be merged to a request from a different cgroup or

it can result in merging of bfqqs for different cgroups or bfqqs of

already dead cgroups and causing possible use-after-free issues. Fix the

problem by updating cgroup information in bfq_merge_bio().

Cc: stable@vger.kernel.org

Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support")

Tested-by: "yukuai (C)" <yukuai3@huawei.com>

Signed-off-by: Jan Kara <jack@suse.cz>

---

 block/bfq-iosched.c | 11 +++++++++--

 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c

index 89fe3f85eb3c..1fc4d4628fba 100644

--- a/block/bfq-iosched.c

+++ b/block/bfq-iosched.c

@@ -2457,10 +2457,17 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,

 	spin_lock_irq(&bfqd->lock);

-	if (bic)

+	if (bic) {

+		/*

+		 * Make sure cgroup info is uptodate for current process before

+		 * considering the merge.

+		 */

+		bfq_bic_update_cgroup(bic, bio);

+

 		bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf));

-	else

+	} else {

 		bfqd->bio_bfqq = NULL;

+	}

 	bfqd->bio_bic = bic;

 	ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);

-- 

2.34.1