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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Fri, 22 Jan 2021 17:10:48 +1100
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Subject: [PATCH] commands/menuentry: Fix quoting in setparams_prefix()
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Commit 9acdcbf32542 (use single quotes in menuentry setparams command)
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says that expressing a quoted single quote will require 3 characters. It
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actually requires (and always did require!) 4 characters:
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str: a'b => a'\''b
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len: 3 => 6 (2 for the letters + 4 for the quote)
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This leads to not allocating enough memory and thus out of bounds writes
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that have been observed to cause heap corruption.
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Allocate 4 bytes for each single quote.
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Commit 22e7dbb2bb81 (Fix quoting in legacy parser.) does the same
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quoting, but it adds 3 as extra overhead on top of the single byte that
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the quote already needs. So it's correct.
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Fixes: CVE-2021-20233
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Fixes: 9acdcbf32542 (use single quotes in menuentry setparams command)
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/commands/menuentry.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/grub-core/commands/menuentry.c b/grub-core/commands/menuentry.c
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index 4b5fcf2ce9a..7a533b9741b 100644
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--- a/grub-core/commands/menuentry.c
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+++ b/grub-core/commands/menuentry.c
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@@ -239,7 +239,7 @@ setparams_prefix (int argc, char **args)
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len += 3; /* 3 = 1 space + 2 quotes */
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p = args[i];
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while (*p)
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- len += (*p++ == '\'' ? 3 : 1);
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+ len += (*p++ == '\'' ? 4 : 1);
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}
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result = grub_malloc (len + 2);
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