linux-kernel - Re: [patch V6 06/11] rseq: Implement syscall entry work for time slice extensions

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Message-ID: <6a0344be-e105-4f09-bf41-02940e730293@efficios.com>
Date: Tue, 16 Dec 2025 10:05:22 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>, Boqun Feng
 <boqun.feng@...il.com>, Jonathan Corbet <corbet@....net>,
 Prakash Sangappa <prakash.sangappa@...cle.com>,
 Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
 K Prateek Nayak <kprateek.nayak@....com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
 Randy Dunlap <rdunlap@...radead.org>, Peter Zijlstra <peterz@...radead.org>,
 Ron Geva <rongevarg@...il.com>, Waiman Long <longman@...hat.com>
Subject: Re: [patch V6 06/11] rseq: Implement syscall entry work for time
 slice extensions

On 2025-12-15 13:24, Thomas Gleixner wrote:
[...]
> 
> If the code detects inconsistent user space that result in a SIGSEGV for
> the application.

With these last updates that allow userspace to call arbitrary system
calls to terminate the grant, the only scenario which triggers SIGSEGV
is if the put_user() storing to the rseq area fails. Perhaps we should
update the wording above to be clearer on which situation triggers
SIGSEGV.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com