Re: [PATCH] audit_tree: keep inode pinned

Re: [PATCH] audit_tree: keep inode pinned

[Richard Guy Briggs]

On 14/11/04, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@suse.cz>

Hi Miklos,

> Audit rules disappear when an inode they watch is evicted from the cache.
> This is likely not what we want.
> 
> The guilty commit is "fsnotify: allow marks to not pin inodes in core",
> which didn't take into account that audit_tree adds watches with a zero
> mask.
> 
> Adding any mask should fix this.

Nice find!  Do you have a quick reproducer to detect this?

> Fixes: 90b1e7a57880 ("fsnotify: allow marks to not pin inodes in core")
> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
> Cc: stable@vger.kernel.org # 2.6.36+
> ---
>  kernel/audit_tree.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -154,6 +154,7 @@ static struct audit_chunk *alloc_chunk(i
>  		chunk->owners[i].index = i;
>  	}
>  	fsnotify_init_mark(&chunk->mark, audit_tree_destroy_watch);
> +	chunk->mark.mask = FS_IN_IGNORED;
>  	return chunk;
>  }
>  

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545

Re: [PATCH] audit_tree: keep inode pinned

[Miklos Szeredi]

On Wed, Nov 5, 2014 at 5:58 PM, Richard Guy Briggs <rgb@redhat.com> wrote:
> On 14/11/04, Miklos Szeredi wrote:
>> From: Miklos Szeredi <mszeredi@suse.cz>
>
> Hi Miklos,
>
>> Audit rules disappear when an inode they watch is evicted from the cache.
>> This is likely not what we want.
>>
>> The guilty commit is "fsnotify: allow marks to not pin inodes in core",
>> which didn't take into account that audit_tree adds watches with a zero
>> mask.
>>
>> Adding any mask should fix this.
>
> Nice find!  Do you have a quick reproducer to detect this?


- reboot
- add tree rule
- echo 2 > /proc/sys/vm/drop_caches

drop_caches doesn't guarantee dropping the inode from the cache, but
after a reboot it usually does.

Thanks,
Miklos

Re: [PATCH] audit_tree: keep inode pinned

[Richard Guy Briggs]

On 14/11/05, Miklos Szeredi wrote:
> On Wed, Nov 5, 2014 at 5:58 PM, Richard Guy Briggs <rgb@redhat.com> wrote:
> > On 14/11/04, Miklos Szeredi wrote:
> >> From: Miklos Szeredi <mszeredi@suse.cz>
> >
> > Hi Miklos,
> >
> >> Audit rules disappear when an inode they watch is evicted from the cache.
> >> This is likely not what we want.
> >>
> >> The guilty commit is "fsnotify: allow marks to not pin inodes in core",
> >> which didn't take into account that audit_tree adds watches with a zero
> >> mask.
> >>
> >> Adding any mask should fix this.
> >
> > Nice find!  Do you have a quick reproducer to detect this?
> 
> - reboot
> - add tree rule
> - echo 2 > /proc/sys/vm/drop_caches
> 
> drop_caches doesn't guarantee dropping the inode from the cache, but
> after a reboot it usually does.

Perfect, thanks!  That works as expected.  While I was at it, I checked
the audit_watch code and the pending "filter on process name" patches to
make sure they didn't have the same problem.

> Thanks,
> Miklos

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545

Re: [PATCH] audit_tree: keep inode pinned

[Paul Moore]

On Tue, Nov 4, 2014 at 5:27 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> From: Miklos Szeredi <mszeredi@suse.cz>
>
> Audit rules disappear when an inode they watch is evicted from the cache.
> This is likely not what we want.
>
> The guilty commit is "fsnotify: allow marks to not pin inodes in core",
> which didn't take into account that audit_tree adds watches with a zero
> mask.
>
> Adding any mask should fix this.
>
> Fixes: 90b1e7a57880 ("fsnotify: allow marks to not pin inodes in core")
> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
> Cc: stable@vger.kernel.org # 2.6.36+
> ---
>  kernel/audit_tree.c |    1 +
>  1 file changed, 1 insertion(+)

Thanks for your help on this, I've merged this into the audit
stable-3.18 branch; I plan on pushing this to Linus later this week.

 * git://git.infradead.org/users/pcmoore/audit stable-3.18

> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -154,6 +154,7 @@ static struct audit_chunk *alloc_chunk(i
>                 chunk->owners[i].index = i;
>         }
>         fsnotify_init_mark(&chunk->mark, audit_tree_destroy_watch);
> +       chunk->mark.mask = FS_IN_IGNORED;
>         return chunk;
>  }

-- 
paul moore
www.paul-moore.com