bochs: Handle failure for potentially large allocations

Some code in the block layer makes potentially huge allocations. Failure
is not completely unexpected there, so avoid aborting qemu and handle
out-of-memory situations gracefully.

This patch addresses the allocations in the bochs block driver.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NBenoit Canet <benoit@irqsave.net>

block/bochs.c

@@ -131,7 +131,11 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
         return -EFBIG;
     }
 
-    s->catalog_bitmap = g_malloc(s->catalog_size * 4);
+    s->catalog_bitmap = g_try_malloc(s->catalog_size * 4);
+    if (s->catalog_size && s->catalog_bitmap == NULL) {
+        error_setg(errp, "Could not allocate memory for catalog");
+        return -ENOMEM;
+    }
 
     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
                      s->catalog_size * 4);