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

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Date: Wed, 29 May 2024 09:04:46 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Andrew Halaney <ahalaney@...hat.com>,
        "Martin
 KaFai Lau" <martin.lau@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Daniel Borkmann <daniel@...earbox.net>, bpf <bpf@...r.kernel.org>
CC: <kernel@...cinc.com>,
        <syzbot+d7b227731ec589e7f4f0@...kaller.appspotmail.com>,
        <syzbot+30a35a2e9c5067cc43fa@...kaller.appspotmail.com>
Subject: Re: [PATCH net] net: validate SO_TXTIME clockid coming from userspace



On 5/29/2024 9:00 AM, Willem de Bruijn wrote:
> Abhishek Chauhan (ABC) wrote:
>>
>>
>> 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. 
> 
> Ah, I missed that.
> Perhaps point directly to the start of that follow-up conversation?
> Thanks Willem, Let me do that when i raise the net-next patch. 
> https://lore.kernel.org/lkml/6bdba7b6-fd22-4ea5-a356-12268674def1@quicinc.com/
> 
>>
>>
>>>> Fixes: 1693c5db6ab8 ("net: Add additional bit to support clockid_t timestamp type")
>>>> Reported-by: syzbot+d7b227731ec589e7f4f0@...kaller.appspotmail.com
>>>> Closes: https://syzkaller.appspot.com/bug?extid=d7b227731ec589e7f4f0
>>>> Reported-by: syzbot+30a35a2e9c5067cc43fa@...kaller.appspotmail.com
>>>> Closes: https://syzkaller.appspot.com/bug?extid=30a35a2e9c5067cc43fa
>>>> Signed-off-by: Abhishek Chauhan <quic_abchauha@...cinc.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.  
>> It is now, but the stricter type definition exists for a reason.
> Try to keep the strict types where possible. Besides aiding
> syntactic checks, it also helps self document code.
Okay i see what you are saying. Makes sense. I will change it to __kernel_clockid_t