kern/164684: [kern][patch] Zero out dynamically allocated sbufs

[Yuri Pankov]

>Number:         164684
>Category:       kern
>Synopsis:       [kern][patch] Zero out dynamically allocated sbufs
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 01 06:30:14 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Yuri Pankov
>Release:        FreeBSD 10.0-CURRENT amd64
>Organization:
>Environment:
System: FreeBSD sirius.xvoid.org 10.0-CURRENT FreeBSD 10.0-CURRENT #1 r230537: Wed Jan 25 16:28:58 MSK 2012 yuri at sirius.xvoid.org:/usr/obj/data/src/freebsd/head/sys/GENERIC amd64
>Description:
Filing this against kernel (as the source is in sys/kern), but got the problem itself using libsbuf - sbuf_newbuf() and sbuf_extend() don't zero out the malloc'ed memory, leading to issues when malloc debugging is enabled.
>How-To-Repeat:
#include <sys/types.h>
#include <sys/sbuf.h>

#include <stdio.h>

int
main(void)
{
        struct sbuf     *sb = sbuf_new_auto();

        sbuf_cat(sb, "TEST TEST");

        printf("s_buf=%s\n", sbuf_data(sb));

        return(0);
}


$ MALLOC_OPTIONS=J ./sbuf
s_buf=TEST TESTâ–’â–’â–’â–’â–’â–’â–’
$ MALLOC_OPTIONS=j ./sbuf
s_buf=TEST TEST
>Fix:
--- sbuf-dynamic.diff begins here ---
Index: sys/kern/subr_sbuf.c
===================================================================
--- sys/kern/subr_sbuf.c	(revision 230853)
+++ sys/kern/subr_sbuf.c	(working copy)
@@ -159,6 +159,7 @@
 	newbuf = SBMALLOC(newsize);
 	if (newbuf == NULL)
 		return (-1);
+	memset(newbuf, 0, newsize);
 	memcpy(newbuf, s->s_buf, s->s_size);
 	if (SBUF_ISDYNAMIC(s))
 		SBFREE(s->s_buf);
@@ -197,6 +198,7 @@
 	s->s_buf = SBMALLOC(s->s_size);
 	if (s->s_buf == NULL)
 		return (NULL);
+	memset(s->s_buf, 0, s->s_size);
 	SBUF_SETFLAG(s, SBUF_DYNAMIC);
 	return (s);
 }
--- sbuf-dynamic.diff ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted: