[PATCH] Fix vfwscanf(3) assignment suppression flag handling bug

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[PATCH] Fix vfwscanf(3) assignment suppression flag handling bug

Lucio Andrés Illanes Albornoz
newlib's vfwscanf(3) (or specifically, __SVFWSCANF_R()) fails to correctly set
the assignment-suppressing character (`*') flag[1] which, when present in the
formatting string, results in undefined behaviour comprising retrieving and
dereferencing a pointer that was not supplied by the caller as such or at all.
When compared to the vfscanf(3) implementation, this would appear to be over
the missing goto match_failure statement preceded by the flags test seen below.
Hence, this patch (re)introduces it.

[1] <http://pubs.opengroup.org/onlinepubs/009695399/functions/fwscanf.html>

--
diff --git a/newlib/libc/stdio/vfwscanf.c b/newlib/libc/stdio/vfwscanf.c
index 0464b0837..ffb6cc85b 100644
--- a/newlib/libc/stdio/vfwscanf.c
+++ b/newlib/libc/stdio/vfwscanf.c
@@ -602,6 +602,7 @@ __SVFWSCANF_R (struct _reent *rptr,
  case L'*':
   if ((flags & (CHAR | SHORT | LONG | LONGDBL | SUPPRESS | MALLOC))
       || width)
+    goto match_failure;
   flags |= SUPPRESS;
   goto again;
  case L'l':
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Re: [PATCH] Fix vfwscanf(3) assignment suppression flag handling bug

Corinna Vinschen
On Jun  1 10:33, Lucio Andrés Illanes Albornoz wrote:
> newlib's vfwscanf(3) (or specifically, __SVFWSCANF_R()) fails to correctly set
> the assignment-suppressing character (`*') flag[1] which, when present in the
> formatting string, results in undefined behaviour comprising retrieving and
> dereferencing a pointer that was not supplied by the caller as such or at all.
> When compared to the vfscanf(3) implementation, this would appear to be over
> the missing goto match_failure statement preceded by the flags test seen below.
> Hence, this patch (re)introduces it.
>
> [1] <http://pubs.opengroup.org/onlinepubs/009695399/functions/fwscanf.html>

Pushed.


Thanks,
Corinna

--
Corinna Vinschen
Cygwin Maintainer
Red Hat

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