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Re: [RFC v2 PATCH] futex: extend set_robust_list to allow 2 locking ABIs at the same time.
- From: Zack Weinberg <zackw at panix dot com>
- To: Thomas Gleixner <tglx at linutronix dot de>
- Cc: "Carlos O'Donell" <carlos at redhat dot com>, Florian Weimer <fweimer at redhat dot com>, Shawn Landden <shawn at git dot icu>, GNU C Library <libc-alpha at sourceware dot org>, linux-api at vger dot kernel dot org, LKML <linux-kernel at vger dot kernel dot org>, Arnd Bergmann <arnd at arndb dot de>, Deepa Dinamani <deepa dot kernel at gmail dot com>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, Catalin Marinas <catalin dot marinas at arm dot com>, Keith Packard <keithp at keithp dot com>, Peter Zijlstra <peterz at infradead dot org>
- Date: Wed, 6 Nov 2019 09:00:51 -0500
- Subject: Re: [RFC v2 PATCH] futex: extend set_robust_list to allow 2 locking ABIs at the same time.
- References: <20191104002909.25783-1-shawn@git.icu> <87woceslfs.fsf@oldenburg2.str.redhat.com> <alpine.DEB.2.21.1911051053470.17054@nanos.tec.linutronix.de> <87sgn2skm6.fsf@oldenburg2.str.redhat.com> <alpine.DEB.2.21.1911051253430.17054@nanos.tec.linutronix.de> <f11d82f1-1e81-e344-3ad2-76e4cb488a3d@redhat.com> <alpine.DEB.2.21.1911051520090.17054@nanos.tec.linutronix.de>
On Tue, Nov 5, 2019 at 9:28 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> The real issue is that the robust list could be circular by incident or
> malice and there is no way for the kernel to figure that out. That would
> prevent the task from exiting and make it iterate over the list until
> doomsday, i.e. a nice unpriviledged DoS.
Why can't the kernel use the standard tortoise-and-hare algorithm for
detecting circular linked lists here?
zw