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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Darren Kenny <darren.kenny@oracle.com>
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Date: Wed, 4 Nov 2020 15:10:51 +0000
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Subject: [PATCH] video/fb/fbfill: Fix potential integer overflow
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The multiplication of 2 unsigned 32-bit integers may overflow before
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promotion to unsigned 64-bit. We should ensure that the multiplication
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is done with overflow detection. Additionally, use grub_sub() for
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subtraction.
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Fixes: CID 73640, CID 73697, CID 73702, CID 73823
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Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
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Signed-off-by: Marco A Benatto <mbenatto@redhat.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/video/fb/fbfill.c | 17 +++++++++++++----
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1 file changed, 13 insertions(+), 4 deletions(-)
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diff --git a/grub-core/video/fb/fbfill.c b/grub-core/video/fb/fbfill.c
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index 11816d07a0b..a37acd1e293 100644
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--- a/grub-core/video/fb/fbfill.c
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+++ b/grub-core/video/fb/fbfill.c
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@@ -31,6 +31,7 @@
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#include <grub/fbfill.h>
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#include <grub/fbutil.h>
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#include <grub/types.h>
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+#include <grub/safemath.h>
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#include <grub/video.h>
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/* Generic filler that works for every supported mode. */
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@@ -61,7 +62,9 @@ grub_video_fbfill_direct32 (struct grub_video_fbblit_info *dst,
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/* Calculate the number of bytes to advance from the end of one line
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to the beginning of the next line. */
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- rowskip = dst->mode_info->pitch - dst->mode_info->bytes_per_pixel * width;
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+ if (grub_mul (dst->mode_info->bytes_per_pixel, width, &rowskip) ||
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+ grub_sub (dst->mode_info->pitch, rowskip, &rowskip))
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+ return;
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/* Get the start address. */
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dstptr = grub_video_fb_get_video_ptr (dst, x, y);
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@@ -98,7 +101,9 @@ grub_video_fbfill_direct24 (struct grub_video_fbblit_info *dst,
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#endif
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/* Calculate the number of bytes to advance from the end of one line
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to the beginning of the next line. */
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- rowskip = dst->mode_info->pitch - dst->mode_info->bytes_per_pixel * width;
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+ if (grub_mul (dst->mode_info->bytes_per_pixel, width, &rowskip) ||
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+ grub_sub (dst->mode_info->pitch, rowskip, &rowskip))
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+ return;
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/* Get the start address. */
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dstptr = grub_video_fb_get_video_ptr (dst, x, y);
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@@ -131,7 +136,9 @@ grub_video_fbfill_direct16 (struct grub_video_fbblit_info *dst,
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/* Calculate the number of bytes to advance from the end of one line
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to the beginning of the next line. */
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- rowskip = (dst->mode_info->pitch - dst->mode_info->bytes_per_pixel * width);
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+ if (grub_mul (dst->mode_info->bytes_per_pixel, width, &rowskip) ||
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+ grub_sub (dst->mode_info->pitch, rowskip, &rowskip))
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+ return;
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/* Get the start address. */
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dstptr = grub_video_fb_get_video_ptr (dst, x, y);
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@@ -161,7 +168,9 @@ grub_video_fbfill_direct8 (struct grub_video_fbblit_info *dst,
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/* Calculate the number of bytes to advance from the end of one line
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to the beginning of the next line. */
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- rowskip = dst->mode_info->pitch - dst->mode_info->bytes_per_pixel * width;
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+ if (grub_mul (dst->mode_info->bytes_per_pixel, width, &rowskip) ||
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+ grub_sub (dst->mode_info->pitch, rowskip, &rowskip))
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+ return;
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/* Get the start address. */
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dstptr = grub_video_fb_get_video_ptr (dst, x, y);
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