linux-kernel - Re: [patch V2 07/50] posix-cpu-timers: Split up posix_cpu_timer

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Message-ID: <87o7a8wdhr.fsf@somnus>
Date: Wed, 17 Apr 2024 11:21:52 +0200
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: Oleg Nesterov <oleg@...hat.com>, Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, Frederic Weisbecker
 <frederic@...nel.org>, John Stultz <jstultz@...gle.com>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Stephen Boyd
 <sboyd@...nel.org>, Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [patch V2 07/50] posix-cpu-timers: Split up posix_cpu_timer_get()

Oleg Nesterov <oleg@...hat.com> writes:

> On 04/11, Thomas Gleixner wrote:
>>
>> In preparation for addressing issues in the timer_get() and timer_set()
>> functions of posix CPU timers.
>
> Cough... I must have missed something, but posix_cpu_timer_get()
> doesn't look right with or without this trivial patch.
>
> It doesn't initialize itp->it_value if cpu_timer_getexpires() == 0,
> this means that sys_timer_gettime() will copy the uninitialized
> cur_setting->it_value on the stack to userspace?

The initialization of itp is already done by the callsites.
do_timer_settime() in posix-timers.c as well as do_cpu_nanosleep() in
posix-cpu-timers.c execute a memset before calling
posix_cpu_timer_get(). So this should be fine - or did I miss something
here?

Thanks,

	Anna-Maria