[PATCH v1] migration: fix RAMBlock add NULL check

[Dmitry Frolov]

qemu_ram_block_from_host() may return NULL, which will be dereferenced w/o
check. Usualy return value is checked for this function.
Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: c7c0e72408df5e7821c0e995122fb2fe0ac001f1 ("migration/ram: Handle RAM 
block resizes during precopy")
Signed-off-by: Dmitry Frolov <fro...@swemel.ru>
---
 migration/ram.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index e4bfd39f08..bd4b7574e1 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4281,6 +4281,11 @@ static void ram_mig_ram_block_resized(RAMBlockNotifier 
*n, void *host,
     RAMBlock *rb = qemu_ram_block_from_host(host, false, &offset);
     Error *err = NULL;
 
+    if (!rb) {
+        error_report("RAM block not found");
+        return;
+    }
+
     if (migrate_ram_is_ignored(rb)) {
         return;
     }
-- 
2.34.1