grub: add a fix for a possible NULL pointer dereference

This change fixes a possible NULL pointer dereference in grub's
EFI support. It is a part of a security series [1].

[1] https://lists.gnu.org/archive/html/grub-devel/2021-03/msg00007.html

(From OE-Core rev: a49ffdd81e020224ea3e94a266e49d40ebb7198a)

Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 66 insertions, 0 deletions

diff --git a/meta/recipes-bsp/grub/files/0007-kern-efi-mm-Fix-possible-NULL-pointer-dereference.patch b/meta/recipes-bsp/grub/files/0007-kern-efi-mm-Fix-possible-NULL-pointer-dereference.patch
new file mode 100644
index 0000000000..d55709406b
--- /dev/null
+++ b/meta/recipes-bsp/grub/files/0007-kern-efi-mm-Fix-possible-NULL-pointer-dereference.patch
@@ -0,0 +1,65 @@
+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)
diff --git a/meta/recipes-bsp/grub/grub2.inc b/meta/recipes-bsp/grub/grub2.inc
index 04ed8b7b23..46d65d8609 100644
--- a/meta/recipes-bsp/grub/grub2.inc
+++ b/meta/recipes-bsp/grub/grub2.inc
@@ -53,6 +53,7 @@ SRC_URI = "${GNU_MIRROR}/grub/grub-${PV}.tar.gz \
            file://0004-kern-parser-Fix-resource-leak-if-argc-0.patch \
            file://0005-efi-Fix-some-malformed-device-path-arithmetic-errors.patch \
            file://0006-kern-efi-Fix-memory-leak-on-failure.patch \
+           file://0007-kern-efi-mm-Fix-possible-NULL-pointer-dereference.patch \
            "
 SRC_URI[md5sum] = "5ce674ca6b2612d8939b9e6abed32934"
 SRC_URI[sha256sum] = "f10c85ae3e204dbaec39ae22fa3c5e99f0665417e91c2cb49b7e5031658ba6ea"