Re: chroot() breaks syslog() ?

[Torsten Foertsch <torsten.foertsch@gmx.net>]

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On Monday 04 August 2003 07:27, Steven Micallef wrote:
> Hi all,
>
> I've stumbled onto what seems to have broken somewhere between 2.4.8 and
> 2.4.18 (sorry, I've been unable to test it on a later version just yet).
> Basically, when using chroot(), syslog() calls don't work.
>
> The following simple example is broken on 2.4.18:
>
> #include    <stdio.h>
> #include    <sys/syslog.h>
>
> int main(void) {
>     chroot("/home/steve");
>     syslog(LOG_ALERT, "TEST");
> }

consider syslogd's -a option. Or simply call openlog(3) with LOG_NDELAY before 
chroot(). Or place the first call to syslog() before chroot(). Syscall() does 
not close the socket between calls.

int main(void) {
  openlog( "klaus", LOG_NDELAY, LOG_NEWS);
  chroot("/tmp");
  printf( "before\n" ); fflush( stdout );
  syslog(LOG_ALERT, "TEST1");
  printf( "between\n" ); fflush( stdout );
  syslog(LOG_ALERT, "TEST2");
}

strace give the following output:

...

socket(PF_UNIX, SOCK_DGRAM, 0)          = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
connect(3, {sin_family=AF_UNIX, path="/dev/log"}, 16) = 0
chroot("/tmp")                          = 0

...

write(1, "before\n", 7before
)                 = 7

...

send(3, "<57>Aug  4 07:17:09 klaus: TEST1", 32, 0) = 32
rt_sigaction(SIGPIPE, {SIG_DFL}, NULL, 8) = 0
write(1, "between\n", 8between
)                = 8

...

send(3, "<57>Aug  4 07:17:09 klaus: TEST2", 32, 0) = 32
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