block, bfq: fix uaf for bfqq in bic_set_bfqq()

After commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'"),
bic->bfqq will be accessed in bic_set_bfqq(), however, in some context
bic->bfqq will be freed, and bic_set_bfqq() is called with the freed
bic->bfqq.

Fix the problem by always freeing bfqq after bic_set_bfqq().

Fixes: 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
Reported-and-tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230130014136.591038-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 7d9b15f0dbd57917aa7d91f42b61ea9c305be2df..0fbde0fc06287ce150cc37125fbb31d103952d15 100644 (file)
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -769,8 +769,8 @@ static void __bfq_bic_change_cgroup(struct bfq_data *bfqd,
                                 * request from the old cgroup.
                                 */
                                bfq_put_cooperator(sync_bfqq);
-                               bfq_release_process_ref(bfqd, sync_bfqq);
                                bic_set_bfqq(bic, NULL, true);
+                               bfq_release_process_ref(bfqd, sync_bfqq);
                        }
                }
        }

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index ccf2204477a57b44a7522fa299dca123d9041278..380e9bda2e57c5652dfe5645504987f749101d36 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5425,9 +5425,11 @@ static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
 
        bfqq = bic_to_bfqq(bic, false);
        if (bfqq) {
-               bfq_release_process_ref(bfqd, bfqq);
+               struct bfq_queue *old_bfqq = bfqq;
+
                bfqq = bfq_get_queue(bfqd, bio, false, bic, true);
                bic_set_bfqq(bic, bfqq, false);
+               bfq_release_process_ref(bfqd, old_bfqq);
        }
 
        bfqq = bic_to_bfqq(bic, true);