[PATCH] hyperv: add check for NULL for msg

[Anastasia Belova]

cpu_physical_memory_map may return NULL in hyperv_hcall_post_message.
Add check for NULL to avoid NULL-dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 76036a5fc7 ("hyperv: process POST_MESSAGE hypercall")
Signed-off-by: Anastasia Belova <abel...@astralinux.ru>
---
 hw/hyperv/hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
index 57b402b956..61c65d7329 100644
--- a/hw/hyperv/hyperv.c
+++ b/hw/hyperv/hyperv.c
@@ -588,7 +588,7 @@ uint16_t hyperv_hcall_post_message(uint64_t param, bool 
fast)
 
     len = sizeof(*msg);
     msg = cpu_physical_memory_map(param, &len, 0);
-    if (len < sizeof(*msg)) {
+    if (!msg || len < sizeof(*msg)) {
         ret = HV_STATUS_INSUFFICIENT_MEMORY;
         goto unmap;
     }
-- 
2.30.2