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| author | Max Reitz | 2017-04-03 19:51:49 +0200 |
|---|---|---|
| committer | Kevin Wolf | 2017-04-07 14:44:05 +0200 |
| commit | 7a25fcd056ddd34ee7abc906c957d252e2889461 (patch) | |
| tree | fe920473168525c8bcb464025ddb665dfbe83189 /block | |
| parent | commit: Set commit_top_bs->total_sectors (diff) | |
| download | qemu-7a25fcd056ddd34ee7abc906c957d252e2889461.tar.gz qemu-7a25fcd056ddd34ee7abc906c957d252e2889461.tar.xz qemu-7a25fcd056ddd34ee7abc906c957d252e2889461.zip | |
block/mirror: Fix use-after-free
If @bs does not have any parents, the only reference to @mirror_top_bs
will be held by the BlockJob object after the bdrv_unref() following
block_job_create(). However, if block_job_create() fails, this reference
will not exist and @mirror_top_bs will have been deleted when we
goto fail.
The issue comes back at all later entries to the fail label: We delete
the BlockJob object before rolling back our changes to the node graph.
This means that we will delete @mirror_top_bs in the process.
All in all, whenever @bs does not have any parents and we go down the
fail path we will dereference @mirror_top_bs after it has been deleted.
Fix this by invoking bdrv_unref() only when block_job_create() was
successful and by bdrv_ref()'ing @mirror_top_bs in the fail path before
deleting the BlockJob object. Finally, bdrv_unref() it at the end of the
fail path after we actually no longer need it.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/mirror.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/block/mirror.c b/block/mirror.c index 9e2fecc15e..46ecd38ef0 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -1150,7 +1150,7 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, mirror_top_bs->total_sectors = bs->total_sectors; /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep - * it alive until block_job_create() even if bs has no parent. */ + * it alive until block_job_create() succeeds even if bs has no parent. */ bdrv_ref(mirror_top_bs); bdrv_drained_begin(bs); bdrv_append(mirror_top_bs, bs, &local_err); @@ -1168,10 +1168,12 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD, speed, creation_flags, cb, opaque, errp); - bdrv_unref(mirror_top_bs); if (!s) { goto fail; } + /* The block job now has a reference to this node */ + bdrv_unref(mirror_top_bs); + s->source = bs; s->mirror_top_bs = mirror_top_bs; @@ -1242,6 +1244,10 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, fail: if (s) { + /* Make sure this BDS does not go away until we have completed the graph + * changes below */ + bdrv_ref(mirror_top_bs); + g_free(s->replaces); blk_unref(s->target); block_job_unref(&s->common); @@ -1250,6 +1256,8 @@ fail: bdrv_child_try_set_perm(mirror_top_bs->backing, 0, BLK_PERM_ALL, &error_abort); bdrv_replace_node(mirror_top_bs, backing_bs(mirror_top_bs), &error_abort); + + bdrv_unref(mirror_top_bs); } void mirror_start(const char *job_id, BlockDriverState *bs, |