From f93c3add3a773e0e3f6277e5517583c4ad3a43c2 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Mon, 14 Oct 2019 17:39:28 +0200 Subject: [PATCH] mirror: Do not dereference invalid pointers mirror_exit_common() may be called twice (if it is called from mirror_prepare() and fails, it will be called from mirror_abort() again). In such a case, many of the pointers in the MirrorBlockJob object will already be freed. This can be seen most reliably for s->target, which is set to NULL (and then dereferenced by blk_bs()). Cc: qemu-stable@nongnu.org Fixes: 737efc1eda23b904fbe0e66b37715fb0e5c3e58b Signed-off-by: Max Reitz Reviewed-by: John Snow Reviewed-by: Vladimir Sementsov-Ogievskiy Message-id: 20191014153931.20699-2-mreitz@redhat.com Signed-off-by: Max Reitz --- block/mirror.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 454365ce00..bb17cfce31 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -620,11 +620,11 @@ static int mirror_exit_common(Job *job) { MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job); BlockJob *bjob = &s->common; - MirrorBDSOpaque *bs_opaque = s->mirror_top_bs->opaque; + MirrorBDSOpaque *bs_opaque; AioContext *replace_aio_context = NULL; - BlockDriverState *src = s->mirror_top_bs->backing->bs; - BlockDriverState *target_bs = blk_bs(s->target); - BlockDriverState *mirror_top_bs = s->mirror_top_bs; + BlockDriverState *src; + BlockDriverState *target_bs; + BlockDriverState *mirror_top_bs; Error *local_err = NULL; bool abort = job->ret < 0; int ret = 0; @@ -634,6 +634,11 @@ static int mirror_exit_common(Job *job) } s->prepared = true; + mirror_top_bs = s->mirror_top_bs; + bs_opaque = mirror_top_bs->opaque; + src = mirror_top_bs->backing->bs; + target_bs = blk_bs(s->target); + if (bdrv_chain_contains(src, target_bs)) { bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs); }