linux-kernel - Re: [patch V5 03/26] posix-timers: Cure si_sys

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Message-ID: <ZxY1ZOZe2FI6xoKX@localhost.localdomain>
Date: Mon, 21 Oct 2024 13:05:08 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	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>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [patch V5 03/26] posix-timers: Cure si_sys_private race

Le Tue, Oct 01, 2024 at 10:42:03AM +0200, Thomas Gleixner a écrit :
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> The si_sys_private member of the siginfo which is embedded in the
> preallocated sigqueue is used by the posix timer code to decide whether a
> timer must be reprogrammed on signal delivery.
> 
> The handling of this is racy as a long standing comment in that code
> documents. It is modified with the timer lock held, but without sighand
> lock being held. The actual signal delivery code checks for it under
> sighand lock without holding the timer lock.
> 
> Hand the new value to send_sigqueue() as argument and store it with sighand
> lock held. This is an intermediate change to address this issue.
> 
> The arguments to this function will be cleanup in subsequent changes.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>