Re: [PATCH 2/2 v2] netlink: kill eff_cap from struct netlink_skb_parms

On Thu, Mar 03, 2011 at 12:15:22PM -0800, Chris Wright wrote:

* David Miller (davem@davemloft.net) wrote:

quoted

From: Chris Wright <redacted>
Date: Thu, 3 Mar 2011 09:32:30 -0800

quoted

* Patrick McHardy (kaber@trash.net) wrote:

quoted

commit 8ff259625f0ab295fa085b0718eed13093813fbc
Author: Patrick McHardy [off-list ref]
Date:   Thu Mar 3 10:17:31 2011 +0100

    netlink: kill eff_cap from struct netlink_skb_parms
    
    Netlink message processing in the kernel is synchronous these days,
    capabilities can be checked directly in security_netlink_recv() from
    the current process.
    
    Signed-off-by: Patrick McHardy [off-list ref]

Thanks for doing that Patrick.  I looked at this earlier and thought
there was still an async path, but I guess that's just to another
userspace process.

BTW, I think you missed a couple connector based callers:

drivers/staging/pohmelfs/config.c:      if (!cap_raised(nsp->eff_cap, CAP_SYS_AD
drivers/video/uvesafb.c:        if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))

Last time I checked, current() for connector based netlink message
consumers was the work queue that is used for connector.

So unless that changed, or my understanding is wrong, current_cap()
inside cn_queue_wrapper(), respectively the d->callback()
will not be the userland sender process' capabilities, but the work
queue capabilities.

If so, then this change introduces the possibility for normal users to
send privileged commands to connector based subsystems, even if they
may not be able to bind() to suitable sockets to receive any replies.

Am I missing something?

	Lars

* Lars Ellenberg (lars.ellenberg@linbit.com) wrote:

Last time I checked, current() for connector based netlink message
consumers was the work queue that is used for connector.

So unless that changed, or my understanding is wrong, current_cap()
inside cn_queue_wrapper(), respectively the d->callback()
will not be the userland sender process' capabilities, but the work
queue capabilities.

Yes, you're right.

If so, then this change introduces the possibility for normal users to
send privileged commands to connector based subsystems, even if they
may not be able to bind() to suitable sockets to receive any replies.

Am I missing something?

No, thanks for review.  This puts back the async issue.

Hi.

On Thu, Mar 03, 2011 at 11:37:46PM +0100, Lars Ellenberg (lars.ellenberg@linbit.com) wrote:

If so, then this change introduces the possibility for normal users to
send privileged commands to connector based subsystems, even if they
may not be able to bind() to suitable sockets to receive any replies.

Am I missing something?

Yup, connector is very async at that place, but I wonder why the hell I
ever made that decision. I believe we can replace it with pure sync call
of the registered connector callback, since netlink is synchronous and
no one has any problem with it.

-- 
	Evgeniy Polyakov

From: Evgeniy Polyakov <redacted>
Date: Fri, 4 Mar 2011 04:29:56 +0300

Hi.

On Thu, Mar 03, 2011 at 11:37:46PM +0100, Lars Ellenberg (lars.ellenberg@linbit.com) wrote:

quoted

If so, then this change introduces the possibility for normal users to
send privileged commands to connector based subsystems, even if they
may not be able to bind() to suitable sockets to receive any replies.

Am I missing something?

Yup, connector is very async at that place, but I wonder why the hell I
ever made that decision. I believe we can replace it with pure sync call
of the registered connector callback, since netlink is synchronous and
no one has any problem with it.

Yes, please it would really help us with what we're trying to do here.

Am 04.03.2011 02:29, schrieb Evgeniy Polyakov:

Hi.

On Thu, Mar 03, 2011 at 11:37:46PM +0100, Lars Ellenberg (lars.ellenberg@linbit.com) wrote:

quoted

If so, then this change introduces the possibility for normal users to
send privileged commands to connector based subsystems, even if they
may not be able to bind() to suitable sockets to receive any replies.

Am I missing something?

Yup, connector is very async at that place, but I wonder why the hell I
ever made that decision. I believe we can replace it with pure sync call
of the registered connector callback, since netlink is synchronous and
no one has any problem with it.

Are you going to do this or do you want me to take care of it?

Hi Patrick.

On Tue, Mar 08, 2011 at 03:50:47PM +0100, Patrick McHardy (kaber@trash.net) wrote:

quoted

Yup, connector is very async at that place, but I wonder why the hell I
ever made that decision. I believe we can replace it with pure sync call
of the registered connector callback, since netlink is synchronous and
no one has any problem with it.

Are you going to do this or do you want me to take care of it?

I will return back at the end of the week and will take care of this
problem. I will not mind if you complete it first though :)

-- 
	Evgeniy Polyakov

Am 08.03.2011 19:32, schrieb Evgeniy Polyakov:

Hi Patrick.

On Tue, Mar 08, 2011 at 03:50:47PM +0100, Patrick McHardy (kaber@trash.net) wrote:

quoted

quoted

Yup, connector is very async at that place, but I wonder why the hell I
ever made that decision. I believe we can replace it with pure sync call
of the registered connector callback, since netlink is synchronous and
no one has any problem with it.

Are you going to do this or do you want me to take care of it?

I will return back at the end of the week and will take care of this
problem. I will not mind if you complete it first though :)

Thanks Evgeniy, I'll give it a shot.

Hi.

On Tue, Mar 08, 2011 at 07:54:33PM +0100, Patrick McHardy (kaber@trash.net) wrote:

quoted

quoted

Are you going to do this or do you want me to take care of it?

I will return back at the end of the week and will take care of this
problem. I will not mind if you complete it first though :)

Thanks Evgeniy, I'll give it a shot.

Is my help needed there or you will clean things up?

-- 
	Evgeniy Polyakov