From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 3 May 2023 16:01:42 +0200 Subject: [PATCH] block: Fix use after free in blockdev_mark_auto_del() job_cancel_locked() drops the job list lock temporarily and it may call aio_poll(). We must assume that the list has changed after this call. Also, with unlucky timing, it can end up freeing the job during job_completed_txn_abort_locked(), making the job pointer invalid, too. For both reasons, we can't just continue at block_job_next_locked(job). Instead, start at the head of the list again after job_cancel_locked() and skip those jobs that we already cancelled (or that are completing anyway). Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Message-Id: <20230503140142.474404-1-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf (cherry-picked from commit e2626874a32602d4e52971c786ef5ffb4430629d) Signed-off-by: Fiona Ebner --- blockdev.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/blockdev.c b/blockdev.c index d7b5c18f0a..2c1752a403 100644 --- a/blockdev.c +++ b/blockdev.c @@ -153,12 +153,22 @@ void blockdev_mark_auto_del(BlockBackend *blk) JOB_LOCK_GUARD(); - for (job = block_job_next_locked(NULL); job; - job = block_job_next_locked(job)) { - if (block_job_has_bdrv(job, blk_bs(blk))) { + do { + job = block_job_next_locked(NULL); + while (job && (job->job.cancelled || + job->job.deferred_to_main_loop || + !block_job_has_bdrv(job, blk_bs(blk)))) + { + job = block_job_next_locked(job); + } + if (job) { + /* + * This drops the job lock temporarily and polls, so we need to + * restart processing the list from the start after this. + */ job_cancel_locked(&job->job, false); } - } + } while (job); dinfo->auto_del = 1; }