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

Message ID 20220330124255.24581-4-jack@suse.cz
State Accepted
Commit ea591cd4eb270393810e7be01feb8fde6a34fbbe
Headers show
Series [1/9] bfq: Avoid false marking of bic as stably merged | expand

Commit Message

Jan Kara March 30, 2022, 12:42 p.m. UTC
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")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 block/bfq-iosched.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
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Patch

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);