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From be03a18b8767be50f16a845c389fd5ed29aae055 Mon Sep 17 00:00:00 2001
From: Darren Kenny <darren.kenny@oracle.com>
Date: Fri, 11 Dec 2020 15:03:13 +0000
Subject: [PATCH] kern/efi/mm: Fix possible NULL pointer dereference
The model of grub_efi_get_memory_map() is that if memory_map is NULL,
then the purpose is to discover how much memory should be allocated to
it for the subsequent call.
The problem here is that with grub_efi_is_finished set to 1, there is no
check at all that the function is being called with a non-NULL memory_map.
While this MAY be true, we shouldn't assume it.
The solution to this is to behave as expected, and if memory_map is NULL,
then don't try to use it and allow memory_map_size to be filled in, and
return 0 as is done later in the code if the buffer is too small (or NULL).
Additionally, drop unneeded ret = 1.
Fixes: CID 96632
Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Upstream-Status: Backport [https://git.savannah.gnu.org/cgit/grub.git/commit/?id=6aee4bfd6973c714056fb7b56890b8d524e94ee1]
Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
---
grub-core/kern/efi/mm.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index b02fab1..5afcef7 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -328,15 +328,24 @@ grub_efi_get_memory_map (grub_efi_uintn_t *memory_map_size,
if (grub_efi_is_finished)
{
int ret = 1;
- if (*memory_map_size < finish_mmap_size)
+
+ if (memory_map != NULL)
{
- grub_memcpy (memory_map, finish_mmap_buf, *memory_map_size);
- ret = 0;
+ if (*memory_map_size < finish_mmap_size)
+ {
+ grub_memcpy (memory_map, finish_mmap_buf, *memory_map_size);
+ ret = 0;
+ }
+ else
+ grub_memcpy (memory_map, finish_mmap_buf, finish_mmap_size);
}
else
{
- grub_memcpy (memory_map, finish_mmap_buf, finish_mmap_size);
- ret = 1;
+ /*
+ * Incomplete, no buffer to copy into, same as
+ * GRUB_EFI_BUFFER_TOO_SMALL below.
+ */
+ ret = 0;
}
*memory_map_size = finish_mmap_size;
if (map_key)
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