linux-kernel - Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info

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Date: Mon, 26 Feb 2024 23:06:55 +0800
From: Wen Yang <wenyang.linux@...mail.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 "Eric W. Biederman" <ebiederm@...ssion.com>,
 Christian Brauner <brauner@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] get_signal: simplify/cleanup the the usage of ksig->info



On 2024/2/26 17:52, Oleg Nesterov wrote:
> OK, lets forget about "no need to initialize ksig->info" part for now.
> 
> Yes, PF_USER_WORKER's never dereference ksig, but I agree this doesn't
> look clean without other cleanups. I'll probably return to this later
> when other pending problems with PF_USER_WORKER are fixed.
> 
> Wen, thanks again for your review.
> 
> Oleg.
> 


Thank you very much, Oleg,

We greatly appreciate your comments and the discussion has given us a 
precious opportunity to understand the linux signal.

--
Best wishes,
Wen


> On 02/23, Oleg Nesterov wrote:
>>
>> On 02/23, Oleg Nesterov wrote:
>>>
>>> On 02/23, Oleg Nesterov wrote:
>>>>
>>>> On 02/23, Wen Yang wrote:
>>>>>
>>>>>
>>>>> On 2024/2/23 18:50, Oleg Nesterov wrote:
>>>>>> +			/*
>>>>>> +			 * implies do_group_exit(), no need to initialize
>>>>>> +			 * ksig->info
>>>>>> +			 */
>>>>>>   			goto fatal;
>>>>>
>>>>> There is little question:
>>>>> If the this conditions is met:
>>>>>     current->flags & PF_USER_WORKER
>>>>> It may execute “goto out“ instead of do_group_exit().
>>>>
>>>> Yes, but vhost/io workers do not use ksig at all.
>>>
>>> Ah, wait...
>>>
>>> I forgot about the ->sa_flags check before hide_si_addr_tag_bits().
>>>
>>> OK, thanks... I'll send V2.
>>
>> Tomorrow.
>>
>> I'll recheck, but I think we need the patch below as 1/2 regadless of
>> this change
>>
>> Oleg.
>> ---
>>
>> --- a/kernel/signal.c
>> +++ b/kernel/signal.c
>> @@ -2897,13 +2897,13 @@ bool get_signal(struct ksignal *ksig)
>>   		/* NOTREACHED */
>>   	}
>>   	spin_unlock_irq(&sighand->siglock);
>> -out:
>> +
>>   	ksig->sig = signr;
>>
>>   	if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
>>   		hide_si_addr_tag_bits(ksig);
>> -
>> -	return ksig->sig > 0;
>> +out:
>> +	return signr > 0;
>>   }
>>
>>   /**
>