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83 lines
3.7 KiB
Diff
83 lines
3.7 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Zhang Boyang <zhangboyang.id@gmail.com>
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Date: Tue, 6 Sep 2022 03:03:21 +0800
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Subject: [PATCH] fbutil: Fix integer overflow
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Expressions like u64 = u32 * u32 are unsafe because their products are
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truncated to u32 even if left hand side is u64. This patch fixes all
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problems like that one in fbutil.
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To get right result not only left hand side have to be u64 but it's also
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necessary to cast at least one of the operands of all leaf operators of
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right hand side to u64, e.g. u64 = u32 * u32 + u32 * u32 should be
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u64 = (u64)u32 * u32 + (u64)u32 * u32.
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For 1-bit bitmaps grub_uint64_t have to be used. It's safe because any
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combination of values in (grub_uint64_t)u32 * u32 + u32 expression will
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not overflow grub_uint64_t.
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Other expressions like ptr + u32 * u32 + u32 * u32 are also vulnerable.
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They should be ptr + (grub_addr_t)u32 * u32 + (grub_addr_t)u32 * u32.
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This patch also adds a comment to grub_video_fb_get_video_ptr() which
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says it's arguments must be valid and no sanity check is performed
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(like its siblings in grub-core/video/fb/fbutil.c).
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Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit 50a11a81bc842c58962244a2dc86bbd31a426e12)
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---
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grub-core/video/fb/fbutil.c | 4 ++--
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include/grub/fbutil.h | 13 +++++++++----
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2 files changed, 11 insertions(+), 6 deletions(-)
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diff --git a/grub-core/video/fb/fbutil.c b/grub-core/video/fb/fbutil.c
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index b98bb51fe8..25ef39f47d 100644
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--- a/grub-core/video/fb/fbutil.c
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+++ b/grub-core/video/fb/fbutil.c
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@@ -67,7 +67,7 @@ get_pixel (struct grub_video_fbblit_info *source,
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case 1:
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if (source->mode_info->blit_format == GRUB_VIDEO_BLIT_FORMAT_1BIT_PACKED)
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{
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- int bit_index = y * source->mode_info->width + x;
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+ grub_uint64_t bit_index = (grub_uint64_t) y * source->mode_info->width + x;
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grub_uint8_t *ptr = source->data + bit_index / 8;
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int bit_pos = 7 - bit_index % 8;
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color = (*ptr >> bit_pos) & 0x01;
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@@ -138,7 +138,7 @@ set_pixel (struct grub_video_fbblit_info *source,
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case 1:
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if (source->mode_info->blit_format == GRUB_VIDEO_BLIT_FORMAT_1BIT_PACKED)
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{
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- int bit_index = y * source->mode_info->width + x;
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+ grub_uint64_t bit_index = (grub_uint64_t) y * source->mode_info->width + x;
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grub_uint8_t *ptr = source->data + bit_index / 8;
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int bit_pos = 7 - bit_index % 8;
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*ptr = (*ptr & ~(1 << bit_pos)) | ((color & 0x01) << bit_pos);
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diff --git a/include/grub/fbutil.h b/include/grub/fbutil.h
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index 4205eb917f..78a1ab3b45 100644
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--- a/include/grub/fbutil.h
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+++ b/include/grub/fbutil.h
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@@ -31,14 +31,19 @@ struct grub_video_fbblit_info
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grub_uint8_t *data;
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};
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-/* Don't use for 1-bit bitmaps, addressing needs to be done at the bit level
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- and it doesn't make sense, in general, to ask for a pointer
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- to a particular pixel's data. */
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+/*
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+ * Don't use for 1-bit bitmaps, addressing needs to be done at the bit level
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+ * and it doesn't make sense, in general, to ask for a pointer
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+ * to a particular pixel's data.
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+ *
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+ * This function assumes that bounds checking has been done in previous phase
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+ * and they are opted out in here.
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+ */
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static inline void *
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grub_video_fb_get_video_ptr (struct grub_video_fbblit_info *source,
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unsigned int x, unsigned int y)
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{
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- return source->data + y * source->mode_info->pitch + x * source->mode_info->bytes_per_pixel;
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+ return source->data + (grub_addr_t) y * source->mode_info->pitch + (grub_addr_t) x * source->mode_info->bytes_per_pixel;
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}
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/* Advance pointer by VAL bytes. If there is no unaligned access available,
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