From 6764579f894950afe87d8ec3b323adde8925d4fd Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 30 Jun 2014 19:03:37 +0100 Subject: [PATCH] block/cow: Avoid use of uninitialized cow_bs in error path Commit 25814e8987 introduced an error-exit code path which does a "goto exit" before the cow_bs variable is initialized, meaning we would call bdrv_unref() on an uninitialized variable and likely segfault. Fix this by moving the NULL-initialization to the top of the function and making the exit code path handle the case where it is NULL. Signed-off-by: Peter Maydell Reviewed-by: Eric Blake Signed-off-by: Stefan Hajnoczi --- block/cow.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/block/cow.c b/block/cow.c index 8f81ee6d56..6ee483327f 100644 --- a/block/cow.c +++ b/block/cow.c @@ -332,7 +332,7 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp) char *image_filename = NULL; Error *local_err = NULL; int ret; - BlockDriverState *cow_bs; + BlockDriverState *cow_bs = NULL; /* Read out options */ image_sectors = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0) / 512; @@ -344,7 +344,6 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp) goto exit; } - cow_bs = NULL; ret = bdrv_open(&cow_bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err); if (ret < 0) { @@ -383,7 +382,9 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp) exit: g_free(image_filename); - bdrv_unref(cow_bs); + if (cow_bs) { + bdrv_unref(cow_bs); + } return ret; }