diff mbox series

[v2,1/4] Fix OOB read in stdlib thousand grouping parsing [BZ #29727]

Message ID ca35ce47afa4a6cb3674f38413061db7635a73ec.1666974807.git.szabolcs.nagy@arm.com
State Committed
Commit 17bfe5954baee1f18672aea94caa1126ec36fb81
Headers
Series patches from the morello port |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Szabolcs Nagy Oct. 28, 2022, 4:39 p.m. UTC 
  __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.

---
v2: - use const thousands_len for !USE_WIDE_CHAR.
---
 stdlib/grouping.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

Comments

Andreas Schwab Nov. 2, 2022, 3:20 p.m. UTC | #1 
On Okt 28 2022, Szabolcs Nagy via Libc-alpha wrote:

> __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.

Ok.
diff mbox series

Patch

diff --git a/stdlib/grouping.c b/stdlib/grouping.c
index be7922f5fd..06cbe7b9c7 100644
--- a/stdlib/grouping.c
+++ b/stdlib/grouping.c
@@ -52,21 +52,19 @@  __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.  */