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From: "Kenneth D. Merry" <ken@FreeBSD.org>
Date: Tue, 7 Jun 2011 05:04:37 +0000 (UTC)
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Subject: svn commit: r222804 - head/sys/kern
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Author: ken
Date: Tue Jun  7 05:04:37 2011
New Revision: 222804
URL: http://svn.freebsd.org/changeset/base/222804

Log:
  Set pca.p_bufr to NULL when we haven't allocated a buffer.
  
  Otherwise, p_bufr is set to garbage on the stack, and if that garbage
  happens to be non-NULL, and the TOLOG or TOCONS flag is set, putbuf()
  will get called and attempt to fill the non-existent buffer.
  
  This is really only relevant for tprintf() (and only when the priority is
  not -1), but set it in uprintf() and ttyprintf() for completeness.
  
  The next step, to avoid log buffer scrambling, would be to add the
  PRINTF_BUFR_SIZE code to tprintf(), but this should prevent panics.
  
  Submitted by:	rmacklem
  Found by:	pho

Modified:
  head/sys/kern/subr_prf.c

Modified: head/sys/kern/subr_prf.c
==============================================================================
--- head/sys/kern/subr_prf.c	Tue Jun  7 04:38:33 2011	(r222803)
+++ head/sys/kern/subr_prf.c	Tue Jun  7 05:04:37 2011	(r222804)
@@ -163,6 +163,7 @@ uprintf(const char *fmt, ...)
 		goto out;
 	}
 	pca.flags = TOTTY;
+	pca.p_bufr = NULL;
 	va_start(ap, fmt);
 	tty_lock(pca.tty);
 	retval = kvprintf(fmt, putchar, &pca, 10, ap);
@@ -206,6 +207,7 @@ tprintf(struct proc *p, int pri, const c
 	pca.pri = pri;
 	pca.tty = tp;
 	pca.flags = flags;
+	pca.p_bufr = NULL;
 	va_start(ap, fmt);
 	if (pca.tty != NULL)
 		tty_lock(pca.tty);
@@ -234,6 +236,7 @@ ttyprintf(struct tty *tp, const char *fm
 	va_start(ap, fmt);
 	pca.tty = tp;
 	pca.flags = TOTTY;
+	pca.p_bufr = NULL;
 	retval = kvprintf(fmt, putchar, &pca, 10, ap);
 	va_end(ap);
 	return (retval);