An error about IPC permission checking

[Robert Watson]

On Sun, 23 Jul 2006, ÀîÉÐ½Ü wrote:

> in the source code kern/sysv_shm.c:
>
> 729         error = ipcperm(td, &shmseg->u.shm_perm, mode);
> 730 #ifdef MAC
> 731         error = mac_check_sysv_shmget(td->td_ucred, shmseg, uap->shmflg);
> 732         if (error != 0)
> 733                 MPRINTF(("mac_check_sysv_shmget returned %d\n", error));
> 734 #endif
> 735         if (error)
> 736                 return (error);
>
> The return value of ipcperm() call is not be checked in time, and 
> interrupted by mac checking, if Mac is enabled.

Indeed, it looks like revision 1.104 was never merged from HEAD to RELENG_6, 
which corrects this bug, and also re-orders the two checks so that the MAC 
check occurs before the DAC check.  I'll go ahead and merge that change.

Thanks,

Robert N M Watson
Computer Laboratory
University of Cambridge