linux-kernel - Re: [PATCH v6 3/4] rseq: Make rseq work with protection keys

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Message-ID: <Z880uLxZn6yfShrB@gmail.com>
Date: Mon, 10 Mar 2025 19:51:36 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Dmitry Vyukov <dvyukov@...gle.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	peterz@...radead.org, boqun.feng@...il.com, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	hpa@...or.com, aruna.ramakrishna@...cle.com, elver@...gle.com,
	"Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 3/4] rseq: Make rseq work with protection keys


* Dmitry Vyukov <dvyukov@...gle.com> wrote:

> > >> If an application registers rseq, and ever switches to another 
> > >> pkey protection (such that the rseq becomes inaccessible), then 
> > >> any context switch will cause failure in 
> > >> __rseq_handle_notify_resume() attempting to read/write struct 
> > >> rseq and/or rseq_cs. Since context switches are asynchronous and 
> > >> are outside of the application control (not part of the 
> > >> restricted code scope), temporarily switch to pkey value that 
> > >> allows access to the 0 (default) PKEY.
> > >>
> > >> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> > >> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> > >> Cc: Peter Zijlstra <peterz@...radead.org>
> > >> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> > >> Cc: Boqun Feng <boqun.feng@...il.com>
> > >> Cc: Thomas Gleixner <tglx@...utronix.de>
> > >> Cc: Ingo Molnar <mingo@...hat.com>
> > >> Cc: Borislav Petkov <bp@...en8.de>
> > >> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > >> Cc: "H. Peter Anvin" <hpa@...or.com>
> > >> Cc: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
> > >> Cc: x86@...nel.org
> > >> Cc: linux-kernel@...r.kernel.org
> > >> Fixes: d7822b1e24f2 ("rseq: Introduce restartable sequences system call")
> > >
> > > Any remaining concerns with this series?
> > >
> > > What tree should it go into?
> >
> > Usually the rseq bits go through the -tip tree.
> 
> Thomas, Ingo, can you please take this to -tip tree? Or who would that be?

I was waiting whether Dave Hansen would have an opinion on this series.

Also, could you please add all the new Reviewed-by tags for the next 
version, plus there was still a bit of a discussion on patch #4, has 
that been resolved?

Thanks,

	Ingo