[newlib-cygwin] cygwin: fix potential buffer overflow in fork

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=1adbd77cab6f60b105c5d8b1a4350161c3ac213d

commit 1adbd77cab6f60b105c5d8b1a4350161c3ac213d
Author: Michael Haubenwallner <michael.haubenwallner@ssi-schaefer.com>
Date:   Mon Oct 9 18:58:24 2017 +0200

    cygwin: fix potential buffer overflow in fork
    
    When fork fails, we can use "%s" now with system_sprintf for the errmsg
    rather than a (potentially too small) buffer for the format string.
    
    * fork.cc (fork): Use "%s" with system_printf now.

Diff:
---
 winsup/cygwin/fork.cc | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/winsup/cygwin/fork.cc b/winsup/cygwin/fork.cc
index 73a72f5..bcbef12 100644
--- a/winsup/cygwin/fork.cc
+++ b/winsup/cygwin/fork.cc
@@ -618,13 +618,8 @@ fork ()
       if (!grouped.errmsg)
 	syscall_printf ("fork failed - child pid %d, errno %d", grouped.child_pid, grouped.this_errno);
       else
-	{
-	  char buf[strlen (grouped.errmsg) + sizeof ("child %d - , errno 4294967295  ")];
-	  strcpy (buf, "child %d - ");
-	  strcat (buf, grouped.errmsg);
-	  strcat (buf, ", errno %d");
-	  system_printf (buf, grouped.child_pid, grouped.this_errno);
-	}
+	system_printf ("child %d - %s, errno %d", grouped.child_pid,
+		       grouped.errmsg, grouped.this_errno);
 
       set_errno (grouped.this_errno);
     }