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From: David Malone <dwmalone@FreeBSD.org>
Date: Wed, 19 Jan 2011 17:17:37 +0000 (UTC)
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Subject: svn commit: r217589 - head/usr.sbin/syslogd
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Author: dwmalone
Date: Wed Jan 19 17:17:37 2011
New Revision: 217589
URL: http://svn.freebsd.org/changeset/base/217589

Log:
  Here v->iov_len has been assigned the return value from snprintf.
  Checking if it is > 0 doesn't make sense, because snprintf returns
  how much space is needed if the buffer is too small. Instead, check
  if the return value was greater than the buffer size, and truncate
  the message if it was too long.
  
  It isn't clear if snprintf can return a negative value in the case
  of an error - I don't believe it can. If it can, then testing
  v->iov_len won't help 'cos it is a size_t, not an ssize_t.
  
  Also, as clang points out, we must always increment v here, because
  later code depends on the message being in iov[5].

Modified:
  head/usr.sbin/syslogd/syslogd.c

Modified: head/usr.sbin/syslogd/syslogd.c
==============================================================================
--- head/usr.sbin/syslogd/syslogd.c	Wed Jan 19 17:11:52 2011	(r217588)
+++ head/usr.sbin/syslogd/syslogd.c	Wed Jan 19 17:17:37 2011	(r217589)
@@ -1093,8 +1093,9 @@ fprintlog(struct filed *f, int flags, co
 		v->iov_len = snprintf(greetings, sizeof greetings,
 		    "\r\n\7Message from syslogd@%s at %.24s ...\r\n",
 		    f->f_prevhost, f->f_lasttime);
-		if (v->iov_len > 0)
-			v++;
+		if (v->iov_len >= sizeof greetings)
+			v->iov_len = sizeof greetings - 1;
+		v++;
 		v->iov_base = nul;
 		v->iov_len = 0;
 		v++;