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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, 28 Oct 2022 21:31:39 +0800
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Subject: [PATCH] normal/charset: Fix an integer overflow in
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grub_unicode_aglomerate_comb()
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The out->ncomb is a bit-field of 8 bits. So, the max possible value is 255.
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However, code in grub_unicode_aglomerate_comb() doesn't check for an
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overflow when incrementing out->ncomb. If out->ncomb is already 255,
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after incrementing it will get 0 instead of 256, and cause illegal
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memory access in subsequent processing.
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This patch introduces GRUB_UNICODE_NCOMB_MAX to represent the max
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acceptable value of ncomb. The code now checks for this limit and
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ignores additional combining characters when limit is reached.
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Reported-by: Daniel Axtens <dja@axtens.net>
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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 da90d62316a3b105d2fbd7334d6521936bd6dcf6)
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---
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grub-core/normal/charset.c | 3 +++
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include/grub/unicode.h | 2 ++
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2 files changed, 5 insertions(+)
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diff --git a/grub-core/normal/charset.c b/grub-core/normal/charset.c
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index 7a5a7c153c..c243ca6dae 100644
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--- a/grub-core/normal/charset.c
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+++ b/grub-core/normal/charset.c
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@@ -472,6 +472,9 @@ grub_unicode_aglomerate_comb (const grub_uint32_t *in, grub_size_t inlen,
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if (!haveout)
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continue;
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+ if (out->ncomb == GRUB_UNICODE_NCOMB_MAX)
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+ continue;
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+
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if (comb_type == GRUB_UNICODE_COMB_MC
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|| comb_type == GRUB_UNICODE_COMB_ME
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|| comb_type == GRUB_UNICODE_COMB_MN)
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diff --git a/include/grub/unicode.h b/include/grub/unicode.h
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index 4de986a857..c4f6fca043 100644
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--- a/include/grub/unicode.h
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+++ b/include/grub/unicode.h
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@@ -147,7 +147,9 @@ struct grub_unicode_glyph
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grub_uint8_t bidi_level:6; /* minimum: 6 */
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enum grub_bidi_type bidi_type:5; /* minimum: :5 */
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+#define GRUB_UNICODE_NCOMB_MAX ((1 << 8) - 1)
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unsigned ncomb:8;
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+
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/* Hint by unicode subsystem how wide this character usually is.
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Real width is determined by font. Set only in UTF-8 stream. */
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int estimated_width:8;
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