diff mbox series

[01/20] Fix OOB read in stdlib thousand grouping parsing [BZ #29727]

Message ID 2650014080d5ad13f0a3968c0c9fd371127b29ca.1666877952.git.szabolcs.nagy@arm.com
State Superseded
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. 27, 2022, 3:32 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.
---
 stdlib/grouping.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Andreas Schwab Oct. 27, 2022, 3:38 p.m. UTC | #1 
On Okt 27 2022, Szabolcs Nagy via Libc-alpha wrote:

> diff --git a/stdlib/grouping.c b/stdlib/grouping.c
> index be7922f5fd..4622897488 100644
> --- a/stdlib/grouping.c
> +++ b/stdlib/grouping.c
> @@ -64,9 +64,17 @@ __correctly_grouped_prefixmb (const STRING_TYPE *begin, const STRING_TYPE *end,
>    thousands_len = strlen (thousands);
>  #endif
>  
> +#ifdef USE_WIDE_CHAR
>    while (end > begin)
> +#else
> +  while (end - begin >= thousands_len)
> +#endif
>      {
> +#ifdef USE_WIDE_CHAR
>        const STRING_TYPE *cp = end - 1;
> +#else
> +      const STRING_TYPE *cp = end - thousands_len;
> +#endif

This could be simplified by defining a constant thousands_len for the
USE_WIDE_CHAR case.
diff mbox series

Patch

diff --git a/stdlib/grouping.c b/stdlib/grouping.c
index be7922f5fd..4622897488 100644
--- a/stdlib/grouping.c
+++ b/stdlib/grouping.c
@@ -64,9 +64,17 @@  __correctly_grouped_prefixmb (const STRING_TYPE *begin, const STRING_TYPE *end,
   thousands_len = strlen (thousands);
 #endif
 
+#ifdef USE_WIDE_CHAR
   while (end > begin)
+#else
+  while (end - begin >= thousands_len)
+#endif
     {
+#ifdef USE_WIDE_CHAR
       const STRING_TYPE *cp = end - 1;
+#else
+      const STRING_TYPE *cp = end - thousands_len;
+#endif
       const char *gp = grouping;
 
       /* Check first group.  */