linux-kernel - Re: [PATCH 4.9.y 1/1] futex: Fix OWNER

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Message-ID: <09cd79ce-291a-1750-6954-ecde0a6bdfcf@huawei.com>
Date:   Thu, 25 Feb 2021 14:29:34 +0800
From:   "Zhengyejian (Zetta)" <zhengyejian1@...wei.com>
To:     Lee Jones <lee.jones@...aro.org>
CC:     <gregkh@...uxfoundation.org>, <stable@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <cj.chengjian@...wei.com>, <judy.chenhui@...wei.com>,
        <zhangjinhao2@...wei.com>
Subject: Re: [PATCH 4.9.y 1/1] futex: Fix OWNER_DEAD fixup



On 2021/2/24 19:19, Lee Jones wrote:
> On Tue, 23 Feb 2021, Zheng Yejian wrote:
> 
>> From: Peter Zijlstra <peterz@...radead.org>
>>
>> commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream.
>>
>> Both Geert and DaveJ reported that the recent futex commit:
>>
>>    c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
>>
>> introduced a problem with setting OWNER_DEAD. We set the bit on an
>> uninitialized variable and then entirely optimize it away as a
>> dead-store.
>>
>> Move the setting of the bit to where it is more useful.
>>
>> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>> Reported-by: Dave Jones <davej@...emonkey.org.uk>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>> Cc: Paul E. McKenney <paulmck@...ibm.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
>> Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net
>> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> 
> Why have you dropped my Reviewed-by?
> 
Really sorry. I thought that a changed patchset needs another review.
Then I do need to append your Reviewed-by and send a "V2" patchset, Do I?

>> ---
>>   kernel/futex.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/futex.c b/kernel/futex.c
>> index b65dbb5d60bb..604d1cb9839d 100644
>> --- a/kernel/futex.c
>> +++ b/kernel/futex.c
>> @@ -2424,9 +2424,6 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
>>   	int err = 0;
>>   
>>   	oldowner = pi_state->owner;
>> -	/* Owner died? */
>> -	if (!pi_state->owner)
>> -		newtid |= FUTEX_OWNER_DIED;
>>   
>>   	/*
>>   	 * We are here because either:
>> @@ -2484,6 +2481,9 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
>>   	}
>>   
>>   	newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
>> +	/* Owner died? */
>> +	if (!pi_state->owner)
>> +		newtid |= FUTEX_OWNER_DIED;
>>   
>>   	if (get_futex_value_locked(&uval, uaddr))
>>   		goto handle_fault;
>