Bug#472549: teapop: NULL dereference in pop_unlock_maildrop

[aCaB]

Package: teapop
Version: 0.3.7-4.2
Severity: important
Tags: patch

Teapop fails to handle unlocking of non existing mboxes in
pop_unlock_maildrop.
This is rather annoying expecially in dotlock mode as the .lock file is
not removed which in turn prevents more messages to be received and
teapop to successfully remove it :p

The problem is located in pop_lock.c, function pop_unlock_maildrop.
First the permissions on the mbox are reset.
        /* Reset permissions on mbox (which might get lost when writing) */
        if (xpinfo->mboxtype == 0) {
                fflush(xpinfo->mbox);
                fchmod(fileno(xpinfo->mbox), xpinfo->mboxperm);
        }

Then the lock is removed:
        /* Only unlock each lock if it's locked */

        if (xpinfo->locktrack & LOCK_DOTLOCK) {
        [...]

However, if the mbox file doesn't exist, xpinfo->mbox is NULL and the
program segfaults on fileno(xpinfo->mbox). The dotlock is therfore never
removed.

Please consider applying the attached patch.

Thanks,
-aCaB

-- System Information:
Debian Release: 4.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.22-4-amd64
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)

*** teapop/pop_lock.c	Mon Mar 24 21:26:54 2008
--- ../../pop_lock.c	Mon Mar 24 21:21:24 2008
***************
*** 331,337 ****
  	sigprocmask(SIG_BLOCK, (sigset_t *)xpinfo->smask, NULL);
  
  	/* Reset permissions on mbox (which might get lost when writing) */
! 	if (xpinfo->mboxtype == 0) {
  		fflush(xpinfo->mbox);
  		fchmod(fileno(xpinfo->mbox), xpinfo->mboxperm);
  	}
--- 331,337 ----
  	sigprocmask(SIG_BLOCK, (sigset_t *)xpinfo->smask, NULL);
  
  	/* Reset permissions on mbox (which might get lost when writing) */
! 	if (xpinfo->mboxtype == 0 && xpinfo->mbox) {
  		fflush(xpinfo->mbox);
  		fchmod(fileno(xpinfo->mbox), xpinfo->mboxperm);
  	}
***************
*** 345,361 ****
  	}
  
  	if (xpinfo->locktrack & LOCK_FLOCK) {
! 		(void)flock(fileno(xpinfo->mbox), LOCK_UN);
  		xpinfo->locktrack &= ~LOCK_FLOCK;
  	}		
  	if (xpinfo->locktrack & LOCK_FCNTL) {
  		lock_data.l_type = F_UNLCK;
  		lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0;
! 		(void)fcntl(fileno(xpinfo->mbox), F_SETLK, &lock_data);
  		xpinfo->locktrack &= ~LOCK_FCNTL;
  	}
  	if (xpinfo->locktrack & LOCK_LOCKF) {
! 		(void)lockf(fileno(xpinfo->mbox), F_ULOCK, 0);
  		xpinfo->locktrack &= ~LOCK_LOCKF;
  	}		
  
--- 345,364 ----
  	}
  
  	if (xpinfo->locktrack & LOCK_FLOCK) {
! 		if (xpinfo->mbox)
! 			(void)flock(fileno(xpinfo->mbox), LOCK_UN);
  		xpinfo->locktrack &= ~LOCK_FLOCK;
  	}		
  	if (xpinfo->locktrack & LOCK_FCNTL) {
  		lock_data.l_type = F_UNLCK;
  		lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0;
! 		if (xpinfo->mbox)
! 			(void)fcntl(fileno(xpinfo->mbox), F_SETLK, &lock_data);
  		xpinfo->locktrack &= ~LOCK_FCNTL;
  	}
  	if (xpinfo->locktrack & LOCK_LOCKF) {
! 		if (xpinfo->mbox)
! 			(void)lockf(fileno(xpinfo->mbox), F_ULOCK, 0);
  		xpinfo->locktrack &= ~LOCK_LOCKF;
  	}