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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: Fri, 5 Aug 2022 00:51:20 +0800
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Subject: [PATCH] font: Fix size overflow in grub_font_get_glyph_internal()
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The length of memory allocation and file read may overflow. This patch
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fixes the problem by using safemath macros.
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There is a lot of code repetition like "(x * y + 7) / 8". It is unsafe
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if overflow happens. This patch introduces grub_video_bitmap_calc_1bpp_bufsz().
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It is safe replacement for such code. It has safemath-like prototype.
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This patch also introduces grub_cast(value, pointer), it casts value to
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typeof(*pointer) then store the value to *pointer. It returns true when
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overflow occurs or false if there is no overflow. The semantics of arguments
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and return value are designed to be consistent with other safemath macros.
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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 941d10ad6f1dcbd12fb613002249e29ba035f985)
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(cherry picked from commit 6bca9693878bdf61dd62b8c784862a48e75f569a)
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---
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grub-core/font/font.c | 17 +++++++++++++----
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include/grub/bitmap.h | 18 ++++++++++++++++++
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include/grub/safemath.h | 2 ++
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3 files changed, 33 insertions(+), 4 deletions(-)
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diff --git a/grub-core/font/font.c b/grub-core/font/font.c
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index 2f09a4a55b..6a3fbebbd8 100644
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--- a/grub-core/font/font.c
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+++ b/grub-core/font/font.c
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@@ -739,7 +739,8 @@ grub_font_get_glyph_internal (grub_font_t font, grub_uint32_t code)
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grub_int16_t xoff;
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grub_int16_t yoff;
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grub_int16_t dwidth;
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- int len;
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+ grub_ssize_t len;
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+ grub_size_t sz;
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if (index_entry->glyph)
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/* Return cached glyph. */
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@@ -768,9 +769,17 @@ grub_font_get_glyph_internal (grub_font_t font, grub_uint32_t code)
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return 0;
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}
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- len = (width * height + 7) / 8;
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- glyph = grub_malloc (sizeof (struct grub_font_glyph) + len);
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- if (!glyph)
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+ /* Calculate real struct size of current glyph. */
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+ if (grub_video_bitmap_calc_1bpp_bufsz (width, height, &len) ||
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+ grub_add (sizeof (struct grub_font_glyph), len, &sz))
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+ {
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+ remove_font (font);
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+ return 0;
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+ }
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+
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+ /* Allocate and initialize the glyph struct. */
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+ glyph = grub_malloc (sz);
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+ if (glyph == NULL)
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{
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remove_font (font);
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return 0;
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diff --git a/include/grub/bitmap.h b/include/grub/bitmap.h
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index 5728f8ca3a..0d9603f619 100644
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--- a/include/grub/bitmap.h
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+++ b/include/grub/bitmap.h
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@@ -23,6 +23,7 @@
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#include <grub/symbol.h>
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#include <grub/types.h>
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#include <grub/video.h>
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+#include <grub/safemath.h>
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struct grub_video_bitmap
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{
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@@ -79,6 +80,23 @@ grub_video_bitmap_get_height (struct grub_video_bitmap *bitmap)
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return bitmap->mode_info.height;
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}
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+/*
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+ * Calculate and store the size of data buffer of 1bit bitmap in result.
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+ * Equivalent to "*result = (width * height + 7) / 8" if no overflow occurs.
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+ * Return true when overflow occurs or false if there is no overflow.
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+ * This function is intentionally implemented as a macro instead of
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+ * an inline function. Although a bit awkward, it preserves data types for
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+ * safemath macros and reduces macro side effects as much as possible.
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+ *
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+ * XXX: Will report false overflow if width * height > UINT64_MAX.
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+ */
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+#define grub_video_bitmap_calc_1bpp_bufsz(width, height, result) \
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+({ \
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+ grub_uint64_t _bitmap_pixels; \
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+ grub_mul ((width), (height), &_bitmap_pixels) ? 1 : \
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+ grub_cast (_bitmap_pixels / GRUB_CHAR_BIT + !!(_bitmap_pixels % GRUB_CHAR_BIT), (result)); \
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+})
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+
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void EXPORT_FUNC (grub_video_bitmap_get_mode_info) (struct grub_video_bitmap *bitmap,
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struct grub_video_mode_info *mode_info);
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diff --git a/include/grub/safemath.h b/include/grub/safemath.h
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index c17b89bba1..bb0f826de1 100644
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--- a/include/grub/safemath.h
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+++ b/include/grub/safemath.h
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@@ -30,6 +30,8 @@
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#define grub_sub(a, b, res) __builtin_sub_overflow(a, b, res)
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#define grub_mul(a, b, res) __builtin_mul_overflow(a, b, res)
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+#define grub_cast(a, res) grub_add ((a), 0, (res))
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+
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#else
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#error gcc 5.1 or newer or clang 3.8 or newer is required
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#endif
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