[PATCH] net_sched: cls_route: remove from list when handle is 0

[PATCH] net_sched: cls_route: remove from list when handle is 0

[Thadeu Lima de Souza Cascardo]

When a route filter is replaced and the old filter has a 0 handle, the old
one won't be removed from the hashtable, while it will still be freed.

The test was there since before commit 1109c00547fc ("net: sched: RCU
cls_route"), when a new filter was not allocated when there was an old one.
The old filter was reused and the reinserting would only be necessary if an
old filter was replaced. That was still wrong for the same case where the
old handle was 0.

Remove the old filter from the list independently from its handle value.

This fixes CVE-2022-2588, also reported as ZDI-CAN-17440.

Reported-by: Zhenpeng Lin <zplin@u.northwestern.edu>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Reviewed-by: Kamal Mostafa <kamal@canonical.com>
Cc: <stable@vger.kernel.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
---
 net/sched/cls_route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c
index a35ab8c27866..3f935cbbaff6 100644
--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -526,7 +526,7 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
 	rcu_assign_pointer(f->next, f1);
 	rcu_assign_pointer(*fp, f);
 
-	if (fold && fold->handle && f->handle != fold->handle) {
+	if (fold) {
 		th = to_hash(fold->handle);
 		h = from_hash(fold->handle >> 16);
 		b = rtnl_dereference(head->table[th]);
-- 
2.34.1

Re: [PATCH] net_sched: cls_route: remove from list when handle is 0

[Jamal Hadi Salim]

On Tue, Aug 9, 2022 at 1:06 PM Thadeu Lima de Souza Cascardo
<cascardo@canonical.com> wrote:
>
> When a route filter is replaced and the old filter has a 0 handle, the old
> one won't be removed from the hashtable, while it will still be freed.
>
> The test was there since before commit 1109c00547fc ("net: sched: RCU
> cls_route"), when a new filter was not allocated when there was an old one.
> The old filter was reused and the reinserting would only be necessary if an
> old filter was replaced. That was still wrong for the same case where the
> old handle was 0.
>
> Remove the old filter from the list independently from its handle value.
>
> This fixes CVE-2022-2588, also reported as ZDI-CAN-17440.
>
> Reported-by: Zhenpeng Lin <zplin@u.northwestern.edu>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> Reviewed-by: Kamal Mostafa <kamal@canonical.com>
> Cc: <stable@vger.kernel.org>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>

Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

cheers,
jamal

Re: [PATCH] net_sched: cls_route: remove from list when handle is 0

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue,  9 Aug 2022 14:05:18 -0300 you wrote:
> When a route filter is replaced and the old filter has a 0 handle, the old
> one won't be removed from the hashtable, while it will still be freed.
> 
> The test was there since before commit 1109c00547fc ("net: sched: RCU
> cls_route"), when a new filter was not allocated when there was an old one.
> The old filter was reused and the reinserting would only be necessary if an
> old filter was replaced. That was still wrong for the same case where the
> old handle was 0.
> 
> [...]

Here is the summary with links:
  - net_sched: cls_route: remove from list when handle is 0
    https://git.kernel.org/netdev/net/c/9ad36309e271

You are awesome, thank you!
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