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From 17bfe5954baee1f18672aea94caa1126ec36fb81 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Tue, 11 Oct 2022 15:24:41 +0100
Subject: [PATCH] Fix OOB read in stdlib thousand grouping parsing [BZ
#29727]
__correctly_grouped_prefixmb only worked with thousands_len == 1,
otherwise it read past the end of cp or thousands.
This affects scanf formats like %'d, %'f and the internal but
exposed __strto{l,ul,f,d,..}_internal with grouping flag set
and an LC_NUMERIC locale where thousands_len > 1.
Avoid OOB access by considering thousands_len when initializing cp.
This fixes bug 29727.
Found by the morello port with strict bounds checking where
FAIL: stdlib/tst-strtod4
FAIL: stdlib/tst-strtod5i
crashed using a locale with thousands_len==3.
---
stdlib/grouping.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/stdlib/grouping.c b/stdlib/grouping.c
index d558d930..e2f31b2a 100644
--- a/stdlib/grouping.c
+++ b/stdlib/grouping.c
@@ -53,21 +53,19 @@ __correctly_grouped_prefixmb (const STRING_TYPE *begin, const STRING_TYPE *end,
#endif
const char *grouping)
{
-#ifndef USE_WIDE_CHAR
- size_t thousands_len;
- int cnt;
-#endif
-
if (grouping == NULL)
return end;
-#ifndef USE_WIDE_CHAR
- thousands_len = strlen (thousands);
+#ifdef USE_WIDE_CHAR
+ size_t thousands_len = 1;
+#else
+ size_t thousands_len = strlen (thousands);
+ int cnt;
#endif
- while (end > begin)
+ while (end - begin >= thousands_len)
{
- const STRING_TYPE *cp = end - 1;
+ const STRING_TYPE *cp = end - thousands_len;
const char *gp = grouping;
/* Check first group. */
--
2.33.0
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