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mirror: Do not dereference invalid pointers

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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: 737efc1eda
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20191014153931.20699-2-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-10-14 17:39:28 +02:00
parent e87a09d625
commit f93c3add3a
1 changed files with 9 additions and 4 deletions
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13
block/mirror.c
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@ -620,11 +620,11 @@ static int mirror_exit_common(Job *job)
{ {
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job); MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
BlockJob *bjob = &s->common; BlockJob *bjob = &s->common;
MirrorBDSOpaque *bs_opaque = s->mirror_top_bs->opaque; MirrorBDSOpaque *bs_opaque;
AioContext *replace_aio_context = NULL; AioContext *replace_aio_context = NULL;
BlockDriverState *src = s->mirror_top_bs->backing->bs; BlockDriverState *src;
BlockDriverState *target_bs = blk_bs(s->target); BlockDriverState *target_bs;
BlockDriverState *mirror_top_bs = s->mirror_top_bs; BlockDriverState *mirror_top_bs;
Error *local_err = NULL; Error *local_err = NULL;
bool abort = job->ret < 0; bool abort = job->ret < 0;
int ret = 0; int ret = 0;
@ -634,6 +634,11 @@ static int mirror_exit_common(Job *job)
} }
s->prepared = true; 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)) { if (bdrv_chain_contains(src, target_bs)) {
bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs); bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs);
} }