[PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[Luiz Capitulino]

From: valis <sec@valis.email>

Commit 76e42ae831991c828cffa8c37736ebfb831ad5ec upstream.

[ Fixed small conflict as 'fnew->ifindex' assignment is not protected by
  CONFIG_NET_CLS_IND on upstream since a51486266c3 ]

When fw_change() is called on an existing filter, the whole
tcf_result struct is always copied into the new instance of the filter.

This causes a problem when updating a filter bound to a class,
as tcf_unbind_filter() is always called on the old instance in the
success path, decreasing filter_cnt of the still referenced class
and allowing it to be deleted, leading to a use-after-free.

Fix this by no longer copying the tcf_result struct from the old filter.

Fixes: e35a8ee5993b ("net: sched: fw use RCU")
Reported-by: valis <sec@valis.email>
Reported-by: Bing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: valis <sec@valis.email>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: M A Ramdhan <ramdhan@starlabs.sg>
Link: https://lore.kernel.org/r/20230729123202.72406-3-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Luiz Capitulino <luizcap@amazon.com>
---
 net/sched/cls_fw.c | 1 -
 1 file changed, 1 deletion(-)

Valis, Greg,

I noticed that 4.14 is missing this fix while we backported all three fixes
from this series to all stable kernels:

https://lore.kernel.org/all/20230729123202.72406-1-jhs@mojatatu.com

Is there a reason to have skipped 4.14 for this fix? It seems we need it.

This is only compiled-tested though, would be good to have a confirmation
from Valis that the issue is present on 4.14 before applying.

- Luiz

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index e63f9c2e37e5..7b04b315b2bd 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -281,7 +281,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
 			return -ENOBUFS;
 
 		fnew->id = f->id;
-		fnew->res = f->res;
 #ifdef CONFIG_NET_CLS_IND
 		fnew->ifindex = f->ifindex;
 #endif /* CONFIG_NET_CLS_IND */
-- 
2.40.1

Re: [PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[valis]

On Mon, Sep 18, 2023 at 8:09 PM Luiz Capitulino <luizcap@amazon.com> wrote:

> Valis, Greg,
>
> I noticed that 4.14 is missing this fix while we backported all three fixes
> from this series to all stable kernels:
>
> https://lore.kernel.org/all/20230729123202.72406-1-jhs@mojatatu.com
>
> Is there a reason to have skipped 4.14 for this fix? It seems we need it.

Hi Luiz!

I see no reason why it should be skipped for 4.14
I've just checked 4.14.325 - it is vulnerable and needs this fix.

Best regards,

valis


>
> This is only compiled-tested though, would be good to have a confirmation
> from Valis that the issue is present on 4.14 before applying.
>
> - Luiz
>
> diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
> index e63f9c2e37e5..7b04b315b2bd 100644
> --- a/net/sched/cls_fw.c
> +++ b/net/sched/cls_fw.c
> @@ -281,7 +281,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
>                         return -ENOBUFS;
>
>                 fnew->id = f->id;
> -               fnew->res = f->res;
>  #ifdef CONFIG_NET_CLS_IND
>                 fnew->ifindex = f->ifindex;
>  #endif /* CONFIG_NET_CLS_IND */
> --
> 2.40.1
>

Re: [PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[Luiz Capitulino]

On 2023-09-18 15:17, valis wrote:

> On Mon, Sep 18, 2023 at 8:09 PM Luiz Capitulino <luizcap@amazon.com> wrote:
> 
>> Valis, Greg,
>>
>> I noticed that 4.14 is missing this fix while we backported all three fixes
>> from this series to all stable kernels:
>>
>> https://lore.kernel.org/all/20230729123202.72406-1-jhs@mojatatu.com
>>
>> Is there a reason to have skipped 4.14 for this fix? It seems we need it.
> 
> Hi Luiz!
> 
> I see no reason why it should be skipped for 4.14
> I've just checked 4.14.325 - it is vulnerable and needs this fix.

Thank you for the quick reply!

- Luiz

> 
> Best regards,
> 
> valis
> 
> 
>>
>> This is only compiled-tested though, would be good to have a confirmation
>> from Valis that the issue is present on 4.14 before applying.
>>
>> - Luiz
>>
>> diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
>> index e63f9c2e37e5..7b04b315b2bd 100644
>> --- a/net/sched/cls_fw.c
>> +++ b/net/sched/cls_fw.c
>> @@ -281,7 +281,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
>>                          return -ENOBUFS;
>>
>>                  fnew->id = f->id;
>> -               fnew->res = f->res;
>>   #ifdef CONFIG_NET_CLS_IND
>>                  fnew->ifindex = f->ifindex;
>>   #endif /* CONFIG_NET_CLS_IND */
>> --
>> 2.40.1
>>

Re: [PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[Harshit Mogalapalli]

Hi Luiz,

On 19/09/23 12:47 am, valis wrote:
> On Mon, Sep 18, 2023 at 8:09 PM Luiz Capitulino <luizcap@amazon.com> wrote:
> 
>> Valis, Greg,
>>
>> I noticed that 4.14 is missing this fix while we backported all three fixes
>> from this series to all stable kernels:
>>
>> https://lore.kernel.org/all/20230729123202.72406-1-jhs@mojatatu.com
>>
>> Is there a reason to have skipped 4.14 for this fix? It seems we need it.
> 
I think we need to apply this to 4.19.y as well.

Your backport patch applies there as well. I compiled the kernel after 
applying your patch to linux-4.19.y's tip.

Thanks,
Harshit
> Hi Luiz!
> 
> I see no reason why it should be skipped for 4.14
> I've just checked 4.14.325 - it is vulnerable and needs this fix.
> 
> Best regards,
> 
> valis
> 
> 
>>
>> This is only compiled-tested though, would be good to have a confirmation
>> from Valis that the issue is present on 4.14 before applying.
>>
>> - Luiz
>>
>> diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
>> index e63f9c2e37e5..7b04b315b2bd 100644
>> --- a/net/sched/cls_fw.c
>> +++ b/net/sched/cls_fw.c
>> @@ -281,7 +281,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
>>                          return -ENOBUFS;
>>
>>                  fnew->id = f->id;
>> -               fnew->res = f->res;
>>   #ifdef CONFIG_NET_CLS_IND
>>                  fnew->ifindex = f->ifindex;
>>   #endif /* CONFIG_NET_CLS_IND */
>> --
>> 2.40.1
>>

Re: [PATH 4.14.y] net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

[Greg KH]

On Mon, Sep 18, 2023 at 06:08:59PM +0000, Luiz Capitulino wrote:
> From: valis <sec@valis.email>
> 
> Commit 76e42ae831991c828cffa8c37736ebfb831ad5ec upstream.
> 
> [ Fixed small conflict as 'fnew->ifindex' assignment is not protected by
>   CONFIG_NET_CLS_IND on upstream since a51486266c3 ]

Now queued up, thanks.

greg k-h