From e6b133311a7a5a618b48c6f38e3c3bb9e9a395c9 Mon Sep 17 00:00:00 2001
From: eillon <yezhenyu2@huawei.com>
Date: Mon, 14 Feb 2022 15:35:28 +0800
Subject: [PATCH] seabios: add check to avoid dereference NULL pointer

alloc_find_lowest() may return NULL, check it.

Signed-off-by: eillon <yezhenyu2@huawei.com>
---
 roms/seabios/src/malloc.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/roms/seabios/src/malloc.c b/roms/seabios/src/malloc.c
index 5827a6523..99fa3b7e0 100644
--- a/roms/seabios/src/malloc.c
+++ b/roms/seabios/src/malloc.c
@@ -544,10 +544,12 @@ malloc_prepboot(void)
 
     // Clear unused f-seg ram.
     struct allocinfo_s *info = alloc_find_lowest(&ZoneFSeg);
-    u32 size = info->range_end - info->range_start;
-    memset(memremap(info->range_start, size), 0, size);
-    dprintf(1, "Space available for UMB: %x-%x, %x-%x\n"
-            , RomEnd, base, info->range_start, info->range_end);
+    if (info) {
+        u32 size = info->range_end - info->range_start;
+        memset(memremap(info->range_start, size), 0, size);
+        dprintf(1, "Space available for UMB: %x-%x, %x-%x\n"
+                , RomEnd, base, info->range_start, info->range_end);
+    }
 
     // We should not give back unused high ram, to support some special
     // guest OS, like oracle linux series.
-- 
2.27.0