[PATCH] fix the %m specifier in syslog

[PATCH] fix the %m specifier in syslog

[Clément Vasseur]

errno must be saved upon vsyslog entry, otherwise its value could be
changed by some libc function before reaching the %m handler in
vsnprintf.
---
 src/misc/syslog.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/misc/syslog.c b/src/misc/syslog.c
index 1cd61ce..57f1d75 100644
--- a/src/misc/syslog.c
+++ b/src/misc/syslog.c
@@ -7,6 +7,7 @@
 #include <signal.h>
 #include <string.h>
 #include <pthread.h>
+#include <errno.h>
 #include "libc.h"
 #include "atomic.h"
 
@@ -76,6 +77,7 @@ static void _vsyslog(int priority, const char *message, va_list ap)
 	time_t now;
 	struct tm tm;
 	char buf[256];
+	int errno_save = errno;
 	int pid;
 	int l, l2;
 
@@ -93,6 +95,7 @@ static void _vsyslog(int priority, const char *message, va_list ap)
 	pid = (log_opt & LOG_PID) ? getpid() : 0;
 	l = snprintf(buf, sizeof buf, "<%d>%s %s%s%.0d%s: ",
 		priority, timebuf, log_ident, "["+!pid, pid, "]"+!pid);
+	errno = errno_save;
 	l2 = vsnprintf(buf+l, sizeof buf - l, message, ap);
 	if (l2 >= 0) {
 		if (l2 >= sizeof buf - l) l = sizeof buf - 1;
-- 
2.0.1

Re: [PATCH] fix the %m specifier in syslog

[Rich Felker]

On Wed, Jul 09, 2014 at 02:34:18PM +0200, Clément Vasseur wrote:
> errno must be saved upon vsyslog entry, otherwise its value could be
> changed by some libc function before reaching the %m handler in
> vsnprintf.

Committed.

Rich

Re: [PATCH] fix the %m specifier in syslog

[Szabolcs Nagy]

* Rich Felker <dalias@libc.org> [2014-07-11 20:04:13 -0400]:
> On Wed, Jul 09, 2014 at 02:34:18PM +0200, Clément Vasseur wrote:
> > errno must be saved upon vsyslog entry, otherwise its value could be
> > changed by some libc function before reaching the %m handler in
> > vsnprintf.
> 
> Committed.

i think the COPYRIGHT file should be updated with new contributors
(it will be harder to track them down later)

Re: [PATCH] fix the %m specifier in syslog

[Rich Felker]

On Sat, Jul 12, 2014 at 08:52:47AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <dalias@libc.org> [2014-07-11 20:04:13 -0400]:
> > On Wed, Jul 09, 2014 at 02:34:18PM +0200, Clément Vasseur wrote:
> > > errno must be saved upon vsyslog entry, otherwise its value could be
> > > changed by some libc function before reaching the %m handler in
> > > vsnprintf.
> > 
> > Committed.
> 
> i think the COPYRIGHT file should be updated with new contributors
> (it will be harder to track them down later)

Yes, but it's actually not as bad as it looks. We can just check the
git log for the last commit to COPYRIGHT then review commits between
then and now. But I agree we should do it more often. Thanks for the
reminder!

Rich