[newlib-cygwin] Fix vfwscanf(3) assignment suppression flag handling bug

[newlib-cygwin] Fix vfwscanf(3) assignment suppression flag handling bug

[Corinna Vinschen]

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https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=d5daede26c651f4e9d6c7abbd2dd2937a1e24e2d

commit d5daede26c651f4e9d6c7abbd2dd2937a1e24e2d
Author: Lucio Andrés Illanes Albornoz <lucio@lucioillanes.de>
Date:   Sat Jun 1 10:33:19 2019 +0200

    Fix vfwscanf(3) assignment suppression flag handling bug
    
    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:
---
 newlib/libc/stdio/vfwscanf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/newlib/libc/stdio/vfwscanf.c b/newlib/libc/stdio/vfwscanf.c
index 0464b08..ffb6cc8 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':