From: Daniel Axtens <d...@axtens.net>
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: 9acdcbf32542 (use single quotes in menuentry setparams command)
Fixes: CVE-2021-20233
Reported-by: Daniel Axtens <d...@axtens.net>
Signed-off-by: Daniel Axtens <d...@axtens.net>
Reviewed-by: Daniel Kiper <daniel.ki...@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 9164df744..720e6d8ea 100644
--- a/grub-core/commands/menuentry.c
+++ b/grub-core/commands/menuentry.c
@@ -230,7 +230,7 @@ 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);
--
2.11.0
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