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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 02:27:05 +0800
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Subject: [PATCH] font: Fix integer overflow in ensure_comb_space()
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In fact it can't overflow at all because glyph_id->ncomb is only 8-bit
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wide. But let's keep safe if somebody changes the width of glyph_id->ncomb
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in the future. This patch also fixes the inconsistency between
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render_max_comb_glyphs and render_combining_glyphs when grub_malloc()
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returns NULL.
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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 b2740b7e4a03bb8331d48b54b119afea76bb9d5f)
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---
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 grub-core/font/font.c | 14 +++++++++-----
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 1 file changed, 9 insertions(+), 5 deletions(-)
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diff --git a/grub-core/font/font.c b/grub-core/font/font.c
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index a115a63b0c..d0e6340404 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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@@ -1468,14 +1468,18 @@ ensure_comb_space (const struct grub_unicode_glyph *glyph_id)
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   if (glyph_id->ncomb <= render_max_comb_glyphs)
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     return;
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-  render_max_comb_glyphs = 2 * glyph_id->ncomb;
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-  if (render_max_comb_glyphs < 8)
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+  if (grub_mul (glyph_id->ncomb, 2, &render_max_comb_glyphs))
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+    render_max_comb_glyphs = 0;
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+  if (render_max_comb_glyphs > 0 && render_max_comb_glyphs < 8)
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     render_max_comb_glyphs = 8;
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   grub_free (render_combining_glyphs);
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-  render_combining_glyphs = grub_malloc (render_max_comb_glyphs
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-					 * sizeof (render_combining_glyphs[0]));
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+  render_combining_glyphs = (render_max_comb_glyphs > 0) ?
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+    grub_calloc (render_max_comb_glyphs, sizeof (render_combining_glyphs[0])) : NULL;
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   if (!render_combining_glyphs)
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-    grub_errno = 0;
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+    {
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+      render_max_comb_glyphs = 0;
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+      grub_errno = GRUB_ERR_NONE;
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+    }
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 }
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 int