Patch "block, bfq: fix uaf for bfqq in bic_set_bfqq()" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-bfq-fix-uaf-for-bfqq-in-bic_set_bfqq.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e6711f08f95034aec1e04ff3e9330e8f48782480
Author: Yu Kuai <yukuai3@xxxxxxxxxx>
Date:   Mon Jan 30 09:41:36 2023 +0800

    block, bfq: fix uaf for bfqq in bic_set_bfqq()
    
    [ Upstream commit b600de2d7d3a16f9007fad1bdae82a3951a26af2 ]
    
    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@xxxxxxx>
    Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Link: https://lore.kernel.org/r/20230130014136.591038-1-yukuai1@xxxxxxxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index dfb6d1d8bd46..60b4299bec8e 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -761,8 +761,8 @@ 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 917939b60ef8..ff9d23889415 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5491,9 +5491,11 @@ 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);