linux-kernel - Re: [PATCH 1/2] futex: adjust a futex timeout with a per-timens offset

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Date:   Thu, 15 Oct 2020 16:13:42 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...il.com>, linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Shuah Khan <shuah@...nel.org>, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] futex: adjust a futex timeout with a per-timens offset

On Thu, Oct 15 2020 at 14:26, Dmitry Safonov wrote:

> On 10/15/20 8:29 AM, Andrei Vagin wrote:
>> For all commands except FUTEX_WAIT, timeout is interpreted as an
>> absolute value. This absolute value is inside the task's time namespace
>> and has to be converted to the host's time.
>> 
>> Cc: <stable@...r.kernel.org>
>> Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens offsets")
>> Reported-by: Hans van der Laan <j.h.vanderlaan@...dent.utwente.nl>
>> Signed-off-by: Andrei Vagin <avagin@...il.com>[..]
>> @@ -3797,6 +3798,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
>>  		t = timespec64_to_ktime(ts);
>>  		if (cmd == FUTEX_WAIT)
>>  			t = ktime_add_safe(ktime_get(), t);
>> +		else if (!(cmd & FUTEX_CLOCK_REALTIME))
>> +			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
>
> Err, it probably should be
> : else if (!(op & FUTEX_CLOCK_REALTIME))

Duh, you are right. I stared at it for a while and did not spot it.

> And there's also
> : SYSCALL_DEFINE6(futex_time32, ...)
> which wants to be patched.

Indeed. I zapped the commits.

Thanks,

        tglx