From: Justin Stitt <justinstitt@google.com>
Date: Thu, 8 Aug 2024 21:43:56 +0000 (-0700)
Subject: lib/string_helpers: rework overflow-dependent code
X-Git-Tag: v6.12-rc1~151^2~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bbf3c7ff9dfa45be51500d23a1276991a7cd8c6e;p=thirdparty%2Flinux.git

lib/string_helpers: rework overflow-dependent code

When @size is 0, the desired behavior is to allow unlimited bytes to be
parsed. Currently, this relies on some intentional arithmetic overflow
where --size gives us SIZE_MAX when size is 0.

Explicitly spell out the desired behavior without relying on intentional
overflow/underflow.

Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240808-b4-string_helpers_caa133-v1-1-686a455167c4@google.com
Signed-off-by: Kees Cook <kees@kernel.org>
---

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 69ba49b853c77..4f887aa62fa0c 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -321,6 +321,9 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
 {
 	char *out = dst;
 
+	if (!size)
+		size = SIZE_MAX;
+
 	while (*src && --size) {
 		if (src[0] == '\\' && src[1] != '\0' && size > 1) {
 			src++;