[Qemu-devel] [PATCH] bdrv_img_create: Fix segfault

[Kevin Wolf <kwolf@redhat.com>]

Block drivers that don't support creating images don't have a size option. Fail
gracefully instead of segfaulting when trying to access the option's value.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index ebd1501..8df2a5f 100644
--- a/block.c
+++ b/block.c
@@ -2900,7 +2900,7 @@ int bdrv_img_create(const char *filename, const char *fmt,
                     char *options, uint64_t img_size, int flags)
 {
     QEMUOptionParameter *param = NULL, *create_options = NULL;
-    QEMUOptionParameter *backing_fmt, *backing_file;
+    QEMUOptionParameter *backing_fmt, *backing_file, *size;
     BlockDriverState *bs = NULL;
     BlockDriver *drv, *proto_drv;
     BlockDriver *backing_drv = NULL;
@@ -2983,7 +2983,8 @@ int bdrv_img_create(const char *filename, const char *fmt,
 
     // The size for the image must always be specified, with one exception:
     // If we are using a backing file, we can obtain the size from there
-    if (get_option_parameter(param, BLOCK_OPT_SIZE)->value.n == -1) {
+    size = get_option_parameter(param, BLOCK_OPT_SIZE);
+    if (size && size->value.n == -1) {
         if (backing_file && backing_file->value.s) {
             uint64_t size;
             char buf[32];
-- 
1.7.5.2