From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Daniel Axtens <dja@axtens.net>

Date: Fri, 22 Jan 2021 17:10:48 +1100

Subject: [PATCH] commands/menuentry: Fix quoting in setparams_prefix()

Commit 9acdcbf32542 (use single quotes in menuentry setparams command)

says that expressing a quoted single quote will require 3 characters. It

actually requires (and always did require!) 4 characters:

  str: a'b => a'\''b

  len:  3  => 6 (2 for the letters + 4 for the quote)

This leads to not allocating enough memory and thus out of bounds writes

that have been observed to cause heap corruption.

Allocate 4 bytes for each single quote.

Commit 22e7dbb2bb81 (Fix quoting in legacy parser.) does the same

quoting, but it adds 3 as extra overhead on top of the single byte that

the quote already needs. So it's correct.

Fixes: CVE-2021-20233

Fixes: 9acdcbf32542 (use single quotes in menuentry setparams command)

Signed-off-by: Daniel Axtens <dja@axtens.net>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

---

 grub-core/commands/menuentry.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grub-core/commands/menuentry.c b/grub-core/commands/menuentry.c

index 4b5fcf2ce9a..7a533b9741b 100644

--- a/grub-core/commands/menuentry.c

+++ b/grub-core/commands/menuentry.c

@@ -239,7 +239,7 @@ setparams_prefix (int argc, char **args)

       len += 3; /* 3 = 1 space + 2 quotes */

       p = args[i];

       while (*p)

-	len += (*p++ == '\'' ? 3 : 1);

+	len += (*p++ == '\'' ? 4 : 1);

     }

   result = grub_malloc (len + 2);