From ea591cd4eb270393810e7be01feb8fde6a34fbbe Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Fri, 1 Apr 2022 12:27:45 +0200
Subject: [PATCH] bfq: Update cgroup information before merging bio
Git-commit: ea591cd4eb270393810e7be01feb8fde6a34fbbe
Patch-mainline: v5.19-rc1
References: git-fixes

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().

(Coly Li: refreshed for Linux v4.12 based SUSE kernel)

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-4-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Coly Li <colyli@suse.de>

---
 block/bfq-iosched.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1854,10 +1854,17 @@ static bool bfq_bio_merge(struct blk_mq_
 
 	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, &free);