linux-kernel - Re: [PATCH v4 02/39] task_work: Fix TWA_NMI_CURRENT race with _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250422121541.1cdacb22@gandalf.local.home>
Date: Tue, 22 Apr 2025 12:15:41 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org, Ingo Molnar
 <mingo@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>, Mark
 Rutland <mark.rutland@....com>, Alexander Shishkin
 <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>, Adrian
 Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, Mark
 Brown <broonie@...nel.org>, linux-toolchains@...r.kernel.org, Jordan Rome
 <jordalgo@...a.com>, Sam James <sam@...too.org>,
 linux-trace-kernel@...r.kernel.org, Andrii Nakryiko
 <andrii.nakryiko@...il.com>, Jens Remus <jremus@...ux.ibm.com>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>, Florian Weimer
 <fweimer@...hat.com>, Andy Lutomirski <luto@...nel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Weinan Liu <wnliu@...gle.com>
Subject: Re: [PATCH v4 02/39] task_work: Fix TWA_NMI_CURRENT race with
 __schedule()

On Wed, 22 Jan 2025 13:42:28 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> If we hit before schedule(), all just works as expected, if we hit after
> schedule(), the task will already have the TIF flag set, and we'll hit
> the return to user path once it gets scheduled again.
> 
> ---
> diff --git a/kernel/task_work.c b/kernel/task_work.c
> index c969f1f26be5..155549c017b2 100644
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -9,7 +9,12 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
>  #ifdef CONFIG_IRQ_WORK
>  static void task_work_set_notify_irq(struct irq_work *entry)
>  {
> -	test_and_set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
> +	/*
> +	 * no-op IPI
> +	 *
> +	 * TWA_NMI_CURRENT will already have set the TIF flag, all
> +	 * this interrupt does it tickle the return-to-user path.
> +	 */
>  }
>  static DEFINE_PER_CPU(struct irq_work, irq_work_NMI_resume) =
>  	IRQ_WORK_INIT_HARD(task_work_set_notify_irq);
> @@ -98,6 +103,7 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
>  		break;
>  #ifdef CONFIG_IRQ_WORK
>  	case TWA_NMI_CURRENT:
> +		set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
>  		irq_work_queue(this_cpu_ptr(&irq_work_NMI_resume));
>  		break;
>  #endif

Does this patch replace patches 1 and 2?

If so, Peter, can you give me a Signed-off-by?

-- Steve