grub: fix a possible integer overflow

This patch adds a fix for a possible integer overflow in grub's
video/fb/video_fb. 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: d15e7cc6fc7de358da2fd1faa8a8ea5bc2fabe98)

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, 40 insertions, 0 deletions

diff --git a/meta/recipes-bsp/grub/files/0034-video-fb-video_fb-Fix-possible-integer-overflow.patch b/meta/recipes-bsp/grub/files/0034-video-fb-video_fb-Fix-possible-integer-overflow.patch
new file mode 100644
index 0000000000..c82b2c7df0
--- /dev/null
+++ b/meta/recipes-bsp/grub/files/0034-video-fb-video_fb-Fix-possible-integer-overflow.patch
@@ -0,0 +1,39 @@
+From aac5574ff340a665ccc78d4c3d61596ac67acbbe Mon Sep 17 00:00:00 2001
+From: Darren Kenny <darren.kenny@oracle.com>
+Date: Fri, 4 Dec 2020 14:51:30 +0000
+Subject: [PATCH] video/fb/video_fb: Fix possible integer overflow
+
+It is minimal possibility that the values being used here will overflow.
+So, change the code to use the safemath function grub_mul() to ensure
+that doesn't happen.
+
+Fixes: CID 73761
+
+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=08413f2f4edec0e2d9bf15f836f6ee5ca2e379cb]
+Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
+---
+ grub-core/video/fb/video_fb.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/grub-core/video/fb/video_fb.c b/grub-core/video/fb/video_fb.c
+index 1c9a138..ae6b89f 100644
+--- a/grub-core/video/fb/video_fb.c
++++ b/grub-core/video/fb/video_fb.c
+@@ -1537,7 +1537,13 @@ doublebuf_pageflipping_init (struct grub_video_mode_info *mode_info,
+                             volatile void *page1_ptr)
+ {
+   grub_err_t err;
+-  grub_size_t page_size = mode_info->pitch * mode_info->height;
++  grub_size_t page_size = 0;
++
++  if (grub_mul (mode_info->pitch, mode_info->height, &page_size))
++    {
++      /* Shouldn't happen, but if it does we've a bug. */
++      return GRUB_ERR_BUG;
++    }
+ 
+   framebuffer.offscreen_buffer = grub_malloc (page_size);
+   if (! framebuffer.offscreen_buffer)
diff --git a/meta/recipes-bsp/grub/grub2.inc b/meta/recipes-bsp/grub/grub2.inc
index 8b5b9e3b3e..04c9b4c092 100644
--- a/meta/recipes-bsp/grub/grub2.inc
+++ b/meta/recipes-bsp/grub/grub2.inc
@@ -80,6 +80,7 @@ SRC_URI = "${GNU_MIRROR}/grub/grub-${PV}.tar.gz \
            file://0031-video-efi_gop-Remove-unnecessary-return-value-of-gru.patch \
            file://0032-video-fb-fbfill-Fix-potential-integer-overflow.patch \
            file://0033-video-fb-video_fb-Fix-multiple-integer-overflows.patch \
+           file://0034-video-fb-video_fb-Fix-possible-integer-overflow.patch \
            "
 SRC_URI[md5sum] = "5ce674ca6b2612d8939b9e6abed32934"
 SRC_URI[sha256sum] = "f10c85ae3e204dbaec39ae22fa3c5e99f0665417e91c2cb49b7e5031658ba6ea"