linux-kernel - Re: PF_USER_WORKERs and shadow stack

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Message-ID: <20250814101247.GC26754@redhat.com>
Date: Thu, 14 Aug 2025 12:12:48 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>, Jens Axboe <axboe@...nel.dk>,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: PF_USER_WORKERs and shadow stack

On 08/13, Dave Hansen wrote:
>
> On 8/13/25 12:14, Oleg Nesterov wrote:
>
> > So I'd like to ensure that ssp_active() can't return T in ssp_get().
> >
> > And... Dave, I understand that it is very easy to criticize someone else's code 😉
> > But - if I am right - the current logic doesn't look clean to me. Regardless.
>
> Hey, I'm all for having "clean" code. But if we're going to add
> complexity (aka. code) to the kernel, we should know what it's getting
> us other than "cleanliness".
>
> BTW, how many PF_USER_WORKER threads _are_ there out there? I wouldn't
> have thought that they were prevalent enough to justify much of an
> effort here.

Agreed. I'll send the patches I have in a minute. To me they don't add
too much complexity and imo they cleanup the changed code.

But! I understand that cleanups are always subjective, so please review
and share your opinion.

Oleg.