misc/169947: System crash via ioctl() on mdctl.

[Jaakko Heinonen]

The following reply was made to PR kern/169947; it has been noted by GNATS.

From: Jaakko Heinonen <jh at FreeBSD.org>
To: Filip Palian <filip.palian at pjwstk.edu.pl>
Cc: bug-followup at FreeBSD.org
Subject: Re: misc/169947: System crash via ioctl() on mdctl.
Date: Wed, 18 Jul 2012 16:33:39 +0300

 On 2012-07-17, Filip Palian wrote:
 > User who has read permission on "/dev/mdctl" is able to crash the
 > system (also within the jail if only provided by devfs(.rules)) via
 > ioctl() handler in "/usr/src/sys/dev/md/md.c:1082". The crash occures
 > in function swap_release_by_cred() (swap_pager.c:285) called in
 > vm_object_deallocate() (md.c:1119). Some detailed information included
 > below.
 > 
 > Patch attached with submission follows:
 > 
 > #include <stdio.h>
 > #include <stdlib.h>
 
 I couldn't reproduce the problem with your test program on current or
 stable/9:
 
 $ ./mdtest.orig 
 say goodnight...
 ioctl(MDIOCATTACH) failed: Invalid argument
 no +r no fun
 
 I tried to modify the test program with following changes but still no
 success.
 
 %%%
 --- mdtest.c	2012-07-18 16:13:34.000000000 +0300
 +++ mdtest.c	2012-07-18 16:17:05.000000000 +0300
 @@ -21,7 +21,8 @@
  	s.md_version = MDIOVERSION;
  	// s.md_type = MD_SWAP;
  	s.md_type = MD_PRELOAD;
 -	s.md_options = MD_CLUSTER | MD_AUTOUNIT | MD_COMPRESS;
 +	s.md_base = -1;
 +	s.md_options = MD_AUTOUNIT;
  
  	// typedef long long = int64 = off_t
  	//s.md_mediasize = 4096*1000000000000000000000000000000000000000000000000000;
 %%%
 
 
 $ ./mdtest 
 say goodnight...
 no +r no fun
 
 A new md device is successfully created.
 
 Are you sure that you attached the correct test program and you didn't
 have local patches applied to your kernel?
 
 -- 
 Jaakko