library/3057: syslog(x, "%%m") does the wrong thing

From: <krh(at)lemniscate.net>
Date: Tue Dec 31 2002 - 20:42:21 EST

>Number: 3057
>Category: library
>Synopsis: syslog(x, "%%m") does the wrong thing
>Confidential: no
net
>Environment:
        

	System      : OpenBSD 3.2
	Architecture: OpenBSD.i386
	Machine     : i386

>Description:

syslog(3) lets the programmer use %m to indicate the current error, as determined by errno. However, it does not check that this percent is not part of some other format conversion (namely %%). So "%%m" does the wrong thing, e.g.:

Dec 31 17:00:27 gauss test3: 3485457128ndefined error: 0

>How-To-Repeat:

#include <stdio.h>
#include <sys/syslog.h>

int
main(void)
{

        syslog(LOG_DEBUG, "%%m");
}
>Fix:

This is against /usr/src/lib/libc/gen/syslog.c in 3.2. It should also work against -current. It is furthermore ugly, but it has been tested, and works. The program shown above now gives:

Dec 31 17:37:35 gauss test3: %m

as it should.

226,230c226,239

< 		if (ch == '%' && fmt[1] == 'm') {
< 			++fmt;
< 			if (data == &sdata) {
< 				prlen = snprintf(t, fmt_left, "%s",
< 				    strerror(saved_errno)); 
---

> 		if (ch == '%') {

> 			if (fmt[1] == 'm') {

> 				++fmt;

> 				if (data == &sdata) {

> 					prlen = snprintf(t, fmt_left, "%s",

> 					    strerror(saved_errno)); 

> 				} else {

> 					prlen = snprintf(t, fmt_left, "Error %d",

> 					    saved_errno); 

> 				}

> 				if (prlen >= fmt_left)

> 					prlen = fmt_left - 1;

> 				t += prlen;

> 				fmt_left -= prlen;

232,233c241,246
< 				prlen = snprintf(t, fmt_left, "Error %d",
< 				    saved_errno); 
---

> 				if (fmt_left > 2) {

> 					*t++ = ch;

> 					*t++ = fmt[1];

> 					fmt_left -= 2;

> 					++fmt;

> 				}

235,238d247
< 			if (prlen >= fmt_left)
< 				prlen = fmt_left - 1;
< 			t += prlen;
< 			fmt_left -= prlen;

>Release-Note:
>Audit-Trail:
>Unformatted:
Received on Wed Jan 1 14:19:04 2003