blockdev: Fix NULL pointer dereference in blockdev-add

If aio=native, we check that cache.direct is set as well. If however
cache wasn't specified at all, qemu just segfaulted.

The old condition didn't make any sense anyway because it effectively
only checked for the default cache mode case, but not for an explicitly
set cache.direct=off mode.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Eric Blake <eblake@redhat.com>

diff --git a/blockdev.c b/blockdev.c
index 561cb816e49dada4a001bd884cbf6d158a258a8b..c3422a1d4193c5dc20cdda17a9d9d0ef38ab7d7f 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -2283,8 +2283,10 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
      *
      * For now, simply forbidding the combination for all drivers will do. */
     if (options->has_aio && options->aio == BLOCKDEV_AIO_OPTIONS_NATIVE) {
-        bool direct = options->cache->has_direct && options->cache->direct;
-        if (!options->has_cache && !direct) {
+        bool direct = options->has_cache &&
+                      options->cache->has_direct &&
+                      options->cache->direct;
+        if (!direct) {
             error_setg(errp, "aio=native requires cache.direct=true");
             goto fail;
         }