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Message-ID: <20160623191123.GE30935@twins.programming.kicks-ass.net> Date: Thu, 23 Jun 2016 21:11:23 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Oleg Nesterov <oleg@...hat.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Andy Lutomirski <luto@...capital.net>, Andy Lutomirski <luto@...nel.org>, the arch/x86 maintainers <x86@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>, Borislav Petkov <bp@...en8.de>, Nadav Amit <nadav.amit@...il.com>, Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Jann Horn <jann@...jh.net>, Heiko Carstens <heiko.carstens@...ibm.com> Subject: Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core) On Thu, Jun 23, 2016 at 04:31:26PM +0200, Oleg Nesterov wrote: > On 06/22, Linus Torvalds wrote: > > > > Oleg, what do you think? Would it be reasonable to free the stack and > > thread_info synchronously at exit time, clear the pointer (to catch > > any odd use), and only RCU-delay the task_struct itself? > > I didn't see the patches yet, quite possibly I misunderstood... But no, > I don't this we can do this (if we are not going to move ti->flags to > task_struct at least). Didn't we talk about using SLAB_DESTROY_BY_RCU for task_struct before? If that is possible, a reuse in per-cpu cache is equally possible. All we really want to guarantee is that the memory remains a task_struct, it need not remain the same task, right?
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