Re: [PATCH net] net: validate SO_TXTIME clockid coming from userspace

["Abhishek Chauhan (ABC)" <quic_abchauha@quicinc.com>]

On 5/29/2024 6:58 AM, Willem de Bruijn wrote:
> minor: double space before userspace
> 
> Abhishek Chauhan wrote:
>> Currently there are no strict checks while setting SO_TXTIME
>> from userspace. With the recent development in skb->tstamp_type
>> clockid with unsupported clocks results in warn_on_once, which causes
>> unnecessary aborts in some systems which enables panic on warns.
>>
>> Add validation in setsockopt to support only CLOCK_REALTIME,
>> CLOCK_MONOTONIC and CLOCK_TAI to be set from userspace.
>>
>> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@linux.dev/
>> Link: https://lore.kernel.org/lkml/20240509211834.3235191-1-quic_abchauha@quicinc.com/
> 
> These discussions can be found directly from the referenced commit?
> If any, I'd like to the conversation we had that arrived at this
> approach.
> 
Not Directly but from the patch series. 
1. First link is for why we introduced skb->tstamp_type 
2. Second link points to the series were we discussed on two approach to solve the problem 
one being limit the skclockid to just TAI,MONO and REALTIME. 



>> Fixes: 1693c5db6ab8 ("net: Add additional bit to support clockid_t timestamp type")
>> Reported-by: syzbot+d7b227731ec589e7f4f0@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=d7b227731ec589e7f4f0
>> Reported-by: syzbot+30a35a2e9c5067cc43fa@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=30a35a2e9c5067cc43fa
>> Signed-off-by: Abhishek Chauhan <quic_abchauha@quicinc.com>
>> ---
>>  net/core/sock.c | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>>
>> diff --git a/net/core/sock.c b/net/core/sock.c
>> index 8629f9aecf91..f8374be9d8c9 100644
>> --- a/net/core/sock.c
>> +++ b/net/core/sock.c
>> @@ -1083,6 +1083,17 @@ bool sockopt_capable(int cap)
>>  }
>>  EXPORT_SYMBOL(sockopt_capable);
>>  
>> +static int sockopt_validate_clockid(int value)
> 
> sock_txtime.clockid has type __kernel_clockid_t.
> 

 __kernel_clockid_t is typedef of int.  

>> +{
>> +	switch (value) {
>> +	case CLOCK_REALTIME:
>> +	case CLOCK_MONOTONIC:
>> +	case CLOCK_TAI:
>> +		return 0;
>> +	}
>> +	return -EINVAL;
>> +}
>> +
>>  /*
>>   *	This is meant for all protocols to use and covers goings on
>>   *	at the socket level. Everything here is generic.
>> @@ -1497,6 +1508,11 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
>>  			ret = -EPERM;
>>  			break;
>>  		}
>> +
>> +		ret = sockopt_validate_clockid(sk_txtime.clockid);
>> +		if (ret)
>> +			break;
>> +
>>  		sock_valbool_flag(sk, SOCK_TXTIME, true);
>>  		sk->sk_clockid = sk_txtime.clockid;
>>  		sk->sk_txtime_deadline_mode =
>> -- 
>> 2.25.1
>>
> 
>