[PATCH] malloc: Add check to avoid dereference NULL pointer.

[likejun (A)]

From: Kejun Li <[e-mail]>

Date: Mon, 22 Mar 2021 14:03:10 +0800

Subject: [PATCH] malloc: Add check to avoid dereference NULL pointer.

info = alloc_find_lowest() may return NULL, should check before

dereference it to avoid potential coredump.

Signed-off-by: Kejun Li <[e-mail]>

---

src/malloc.c | 10 ++++++----

1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/malloc.c b/src/malloc.c index 3733855..d355b77 100644

--- a/src/malloc.c

+++ b/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);

+    }

// Give back unused high ram.

info = alloc_find_lowest(&ZoneHigh);

2.19.1

[Kevin O'Connor]

On Tue, Mar 23, 2021 at 03:03:37AM +0000, likejun (A) wrote:
> From: Kejun Li <[e-mail]>
>
> Date: Mon, 22 Mar 2021 14:03:10 +0800
>
> Subject: [PATCH] malloc: Add check to avoid dereference NULL pointer.
>
> info = alloc_find_lowest() may return NULL, should check before
>
> dereference it to avoid potential coredump.

I don't see any case where info could be NULL - there has to be space
in the ZoneFSeg or SeaBIOS wont function at all.

-Kevin