[PULL for-4.2 3/3] block/file-posix: Fix laio_init() error handling crash bug

[Markus Armbruster]

raw_aio_attach_aio_context() passes uninitialized Error *local_err by
reference to laio_init() via aio_setup_linux_aio().  When laio_init()
fails, it passes it on to error_setg_errno(), tripping error_setv()'s
assertion unless @local_err is null by dumb luck.

Fix by initializing @local_err properly.

Fixes: ed6e2161715c527330f936d44af4c547f25f687e
Cc: Nishanth Aravamudan <address@hidden>
Cc: Stefan Hajnoczi <address@hidden>
Cc: Kevin Wolf <address@hidden>
Signed-off-by: Markus Armbruster <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Kevin Wolf <address@hidden>
---
 block/file-posix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 1f0f61a02b..1b805bd938 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1973,7 +1973,7 @@ static void raw_aio_attach_aio_context(BlockDriverState 
*bs,
 #ifdef CONFIG_LINUX_AIO
     BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
-        Error *local_err;
+        Error *local_err = NULL;
         if (!aio_setup_linux_aio(new_context, &local_err)) {
             error_reportf_err(local_err, "Unable to use native AIO, "
                                          "falling back to thread pool: ");
-- 
2.21.0