From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70F2FC4332F for ; Tue, 18 Jan 2022 06:59:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244313AbiARG7G (ORCPT ); Tue, 18 Jan 2022 01:59:06 -0500 Received: from helcar.hmeau.com ([216.24.177.18]:59644 "EHLO fornost.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230196AbiARG7E (ORCPT ); Tue, 18 Jan 2022 01:59:04 -0500 Received: from gwarestrin.arnor.me.apana.org.au ([192.168.103.7]) by fornost.hmeau.com with smtp (Exim 4.92 #5 (Debian)) id 1n9iRd-0007cI-7l; Tue, 18 Jan 2022 17:58:18 +1100 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Tue, 18 Jan 2022 17:58:17 +1100 Date: Tue, 18 Jan 2022 17:58:17 +1100 From: Herbert Xu To: Linus Torvalds Cc: ebiggers@kernel.org, surenb@google.com, hannes@cmpxchg.org, tj@kernel.org, lizefan.x@bytedance.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, stable@vger.kernel.org, kernel-team@android.com, syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Subject: Re: [PATCH v2 1/1] psi: Fix uaf issue when psi trigger is destroyed while being polled Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Newsgroups: apana.lists.os.linux.doc,apana.lists.os.linux.kernel Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds wrote: > > Of course, in practice, for pointers, the whole "dereference off a > pointer" on the read side *does* imply a barrier in all relevant > situations. So yes, a smp_store_release() -> READ_ONCE() does work in > practice, although it's technically wrong (in particular, it's wrong > on alpha, because of the completely broken memory ordering that alpha > has that doesn't even honor data dependencies as read-side orderings) READ_ONCE has contained the alpha barrier since 2017: commit 76ebbe78f7390aee075a7f3768af197ded1bdfbb Author: Will Deacon Date: Tue Oct 24 11:22:47 2017 +0100 locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE() Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt