[PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Jamal Hadi Salim]

Follows up on:
https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/

handle of 0 implies from/to of universe realm which is not very
sensible.

Lets see what this patch will do:
$sudo tc qdisc add dev $DEV root handle 1:0 prio

//lets manufacture a way to insert handle of 0
$sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 \
route to 0 from 0 classid 1:10 action ok

//gets rejected...
Error: handle of 0 is not valid.
We have an error talking to the kernel, -1

//lets create a legit entry..
sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 route from 10 \
classid 1:10 action ok

//what did the kernel insert?
$sudo tc filter ls dev $DEV parent 1:0
filter protocol ip pref 100 route chain 0
filter protocol ip pref 100 route chain 0 fh 0x000a8000 flowid 1:10 from 10
	action order 1: gact action pass
	 random type none pass val 0
	 index 1 ref 1 bind 1

//Lets try to replace that legit entry with a handle of 0
$ sudo tc filter replace dev $DEV parent 1:0 protocol ip prio 100 \
handle 0x000a8000 route to 0 from 0 classid 1:10 action drop

Error: Replacing with handle of 0 is invalid.
We have an error talking to the kernel, -1

And last, lets run Cascardo's POC:
$ ./poc
0
0
-22
-22
-22

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
---
 net/sched/cls_route.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c
index 3f935cbbaff6..48712bc51bda 100644
--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -424,6 +424,11 @@ static int route4_set_parms(struct net *net, struct tcf_proto *tp,
 			return -EINVAL;
 	}
 
+	if (!nhandle) {
+		NL_SET_ERR_MSG(extack, "Replacing with handle of 0 is invalid");
+		return -EINVAL;
+	}
+
 	h1 = to_hash(nhandle);
 	b = rtnl_dereference(head->table[h1]);
 	if (!b) {
@@ -477,6 +482,11 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
 	int err;
 	bool new = true;
 
+	if (!handle) {
+		NL_SET_ERR_MSG(extack, "Creating with handle of 0 is invalid");
+		return -EINVAL;
+	}
+
 	if (opt == NULL)
 		return handle ? -EINVAL : 0;
 
-- 
2.25.1

Re: [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Stephen Hemminger]

On Sun, 14 Aug 2022 11:27:58 +0000
Jamal Hadi Salim <jhs@mojatatu.com> wrote:

> Follows up on:
> https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
> 
> handle of 0 implies from/to of universe realm which is not very
> sensible.
> 
> Lets see what this patch will do:
> $sudo tc qdisc add dev $DEV root handle 1:0 prio
> 
> //lets manufacture a way to insert handle of 0
> $sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 \
> route to 0 from 0 classid 1:10 action ok
> 
> //gets rejected...
> Error: handle of 0 is not valid.
> We have an error talking to the kernel, -1
> 
> //lets create a legit entry..
> sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 route from 10 \
> classid 1:10 action ok
> 
> //what did the kernel insert?
> $sudo tc filter ls dev $DEV parent 1:0
> filter protocol ip pref 100 route chain 0
> filter protocol ip pref 100 route chain 0 fh 0x000a8000 flowid 1:10 from 10
> 	action order 1: gact action pass
> 	 random type none pass val 0
> 	 index 1 ref 1 bind 1
> 
> //Lets try to replace that legit entry with a handle of 0
> $ sudo tc filter replace dev $DEV parent 1:0 protocol ip prio 100 \
> handle 0x000a8000 route to 0 from 0 classid 1:10 action drop
> 
> Error: Replacing with handle of 0 is invalid.
> We have an error talking to the kernel, -1
> 
> And last, lets run Cascardo's POC:
> $ ./poc
> 0
> 0
> -22
> -22
> -22
> 
> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>

Acked-by: Stephen Hemminger <stephen@networkplumber.org>

Re: [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Sun, 14 Aug 2022 11:27:58 +0000 you wrote:
> Follows up on:
> https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
> 
> handle of 0 implies from/to of universe realm which is not very
> sensible.
> 
> Lets see what this patch will do:
> $sudo tc qdisc add dev $DEV root handle 1:0 prio
> 
> [...]

Here is the summary with links:
  - [net,1/1] net_sched: cls_route: disallow handle of 0
    https://git.kernel.org/netdev/net/c/02799571714d

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Jakub Kicinski]

On Sun, 14 Aug 2022 11:27:58 +0000 Jamal Hadi Salim wrote:
> Follows up on:
> https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
> 
> handle of 0 implies from/to of universe realm which is not very
> sensible.

Heh, I was gonna say, but then you acked the other fix :)

Re: [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Jamal Hadi Salim]

The earlier discussion was to let the other fix in to plug the CVE
hole (I had proposed
disallowing handle of 0 in that discussion).

cheers,
jamal

On Mon, Aug 15, 2022 at 1:44 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Sun, 14 Aug 2022 11:27:58 +0000 Jamal Hadi Salim wrote:
> > Follows up on:
> > https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
> >
> > handle of 0 implies from/to of universe realm which is not very
> > sensible.
>
> Heh, I was gonna say, but then you acked the other fix :)

Re: [vs-plain] [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Anthony Liguori]

Jamal Hadi Salim <jhs@mojatatu.com> writes:

> Follows up on:
> https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
>
> handle of 0 implies from/to of universe realm which is not very
> sensible.

Hi,

This was posted two weeks ago and now that it's merged, could you please
post to oss-security?

I don't think there was an actual embargo on this one.

Regards,

Anthony Liguori

Re: [vs-plain] [PATCH net 1/1] net_sched: cls_route: disallow handle of 0

[Jamal Hadi Salim]

On Mon, Aug 29, 2022 at 11:26 AM Anthony Liguori <aliguori@amazon.com> wrote:
>
> Jamal Hadi Salim <jhs@mojatatu.com> writes:
>
> > Follows up on:
> > https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
> >
> > handle of 0 implies from/to of universe realm which is not very
> > sensible.
>
> Hi,
>
> This was posted two weeks ago and now that it's merged, could you please
> post to oss-security?
>
> I don't think there was an actual embargo on this one.
>

Apologies, not familiar with the process and wasnt sure if this was
addressed to me.
Are you asking for this to be cross-posted to oss-security?

cheers,
jamal