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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9AE47D116F3 for ; Sat, 29 Nov 2025 08:54:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=N5Hf/oCoaC+bmr5nJVcUOjG4GACNlaY1TCA6/nmAPjE=; b=1WZzQteGywkYlIx9AzqxcNM17H Pr01DwS1y7FQCF8fK3sLzbZz+MLE20F1IizdjwPI75seWON5soeTizRsRwc3rLw0uWTSHJDltUhhE PVQICDb2RSgNTEIhcX/4apT8iQaTeyUeLSphP1BqKThAZUBr8JuLp211WEMQ59JmGKoA4PvrXMQJb s7hiEBJXHKx8ZhAqhQeklOdhfT6Ezur1FkJmE94FQCYuWKD1Q2xGj5vmZVaB6ebXS5SC/d6hG2bRO Cu+ipMKIzVA4xdPYNI3lC9ULdje06AlPV0r3DYPsKhvfmRvMdSVTQ++HwLyuHCmaTXUvarKt8EUCU T1H2e4Gg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vPGik-00000001P4U-06c0; Sat, 29 Nov 2025 08:54:22 +0000 Received: from zeniv.linux.org.uk ([2a03:a000:7:0:5054:ff:fe1c:15ff]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vPGih-00000001P44-1xHl for linux-arm-kernel@lists.infradead.org; Sat, 29 Nov 2025 08:54:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=N5Hf/oCoaC+bmr5nJVcUOjG4GACNlaY1TCA6/nmAPjE=; b=PTjftmI8M0fFYykNkkoVgNwvZe sRl0yPdorZlBO7dqb9b2+56JO6cvDqq+27j4S4lAbjt0IfK906dSV0JHKIF6oUAcZh7F+1I9OXyXN 6yRPprKZfRAggthT4NsG5xgCJhC8j4GQ9Y0hCbf/btIVPJ7aUN2sWaFQ1aXkZrmx7iSZU4M6KA5i1 VpjlZA9tKeXauh5uTQb1RaTc10dAEnvXoJRgc3j3+Qj591X0teehEUGcHrjh3OQWbF6S0017Ao1VM /Vau/quGQchFyHIe6X16LLSWuE5UEd5iDmwgbHYeivqdZVuX9//YAH6hMECm1fPh6ioRSJEV6mVbY teD+rj7Q==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.99 #2 (Red Hat Linux)) id 1vPGid-00000007Cs0-3WJq; Sat, 29 Nov 2025 08:54:15 +0000 Date: Sat, 29 Nov 2025 08:54:15 +0000 From: Al Viro To: Linus Torvalds Cc: Zizhi Wo , "Russell King (Oracle)" , Catalin Marinas , Will Deacon , jack@suse.com, brauner@kernel.org, hch@lst.de, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, yangerkun@huawei.com, wangkefeng.wang@huawei.com, pangliyuan1@huawei.com, xieyuanbin1@huawei.com Subject: Re: [Bug report] hash_name() may cross page boundary and trigger sleep in RCU context Message-ID: <20251129085415.GJ3538@ZenIV> References: <20251126090505.3057219-1-wozizhi@huaweicloud.com> <33ab4aef-020e-49e7-8539-31bf78dac61a@huaweicloud.com> <3d590a6d-07d1-433c-add1-8b7d53018854@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251129_005419_506604_CCE1EBD9 X-CRM114-Status: GOOD ( 15.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 28, 2025 at 05:35:37PM -0800, Linus Torvalds wrote: > On Fri, 28 Nov 2025 at 17:01, Zizhi Wo wrote: > > > > Thank you for your answer. In fact, this solution is similar to the one > > provided by Al. > > Hmm. I'm not seeing the replies from Al for some reason. Maybe he didn't cc me. Sorry, I thought you've been somewhere in that Cc, should've verified that. > That said, somebody should definitely double-check me - because I > think arm also did the vdso trick at high addresses that i386 used to > do, so there is the fake VDSO thing up there. > > But if you get a page fault on that, it's not going to be fixed up, so > even if user space can access it, there's no point in looking that > fake vm area up for page faults. gate_vma is not inserted anywhere - it's special-cased in coredump_next_vma(), proc_get_vma() and get_gate_page(); none of that can lead to insertion. AFAICS its uses in mlock_fixup(), __mmap_complete() and should_skip_vam() are pure paranoia - "if we somehow ended up running into gate_vma, let's make sure we don't screw it over" and had always been that way. So VMA lookup would get NULL.