linux-kernel - Re: [PATCH net] dccp: check for ccid in ccid_hc_tx_send

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Date:   Mon, 30 Oct 2023 21:10:21 +0530
From:   Bragatheswaran Manickavel <bragathemanick0908@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        dccp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+c71bc336c5061153b502@...kaller.appspotmail.com
Subject: Re: [PATCH net] dccp: check for ccid in ccid_hc_tx_send_packet


On 30/10/23 14:29, Eric Dumazet wrote:
> On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
> <bragathemanick0908@...il.com> wrote:
>> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
>> leading to a NULL pointer dereference
>>
>> Below mentioned commit has similarly changes
>> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
>>
>> Reported-by: syzbot+c71bc336c5061153b502@...kaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
>> Signed-off-by: Bragatheswaran Manickavel <bragathemanick0908@...il.com>
>> ---
>>   net/dccp/ccid.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
>> index 105f3734dadb..1015dc2b9392 100644
>> --- a/net/dccp/ccid.h
>> +++ b/net/dccp/ccid.h
>> @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
>>   static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
>>                                           struct sk_buff *skb)
>>   {
>> -       if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
>> +       if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
>>                  return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
>>          return CCID_PACKET_SEND_AT_ONCE;
>>   }
>> --
>> 2.34.1
>>
> If you are willing to fix dccp, I would make sure that some of
> lockless accesses to dccps_hc_tx_ccid
> are also double checked and fixed.
>
> do_dccp_getsockopt() and dccp_get_info()


Hi Eric,

In both do_dccp_getsockopt() and dccp_get_info(), dccps_hc_rx_ccid are 
checked properly before access.

Thanks,
Bragathe