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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC742C4332F for ; Fri, 18 Nov 2022 17:03:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0C52B6B0071; Fri, 18 Nov 2022 12:03:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0766A6B0072; Fri, 18 Nov 2022 12:03:06 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E58968E0001; Fri, 18 Nov 2022 12:03:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D541B6B0071 for ; Fri, 18 Nov 2022 12:03:05 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 9ECA012138E for ; Fri, 18 Nov 2022 17:03:05 +0000 (UTC) X-FDA: 80147183130.08.121F9F6 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf20.hostedemail.com (Postfix) with ESMTP id 5C7A01C0028 for ; Fri, 18 Nov 2022 17:03:03 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id D4BF31FDA4; Fri, 18 Nov 2022 17:03:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1668790981; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fK2sdLfZqlxwdzyzeVC6Yy7wx8vYkqbsaxCq7BgcB58=; b=LS+hNeQ4geGgj4IXWO5+0pS41T+O+kbhrtYk+pP+vVRIoeuKs+oW13F6Ht+tR7USTuEyYF w44h38vtDK2kFPU+O2RCals0tqkM1nJKUf86qC24NucyatqLyr4TTvgkMY8PsBAD2uBX+L cHUUR5s7utA0uOsl3r11W1mUfWblbh8= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1668790981; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fK2sdLfZqlxwdzyzeVC6Yy7wx8vYkqbsaxCq7BgcB58=; b=khb2AjlSZXqyWGI6UYbr+/ZmYWHGQEHMU8He9yK4yvl4DWCKZ0jYtp3ha5rFTfTmR/yC2u C7/yrrNfpsGvyLBA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 41DED1345B; Fri, 18 Nov 2022 17:03:01 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id kEZlD8W6d2PfGAAAMHmgww (envelope-from ); Fri, 18 Nov 2022 17:03:01 +0000 Message-ID: Date: Fri, 18 Nov 2022 18:03:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH mm-unstable v1 05/20] mm: add early FAULT_FLAG_WRITE consistency checks Content-Language: en-US To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Matthew Wilcox , Mike Kravetz , Muchun Song , Shuah Khan , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann , Christoph Hellwig , Alex Williamson References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-6-david@redhat.com> From: Vlastimil Babka In-Reply-To: <20221116102659.70287-6-david@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668790983; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=fK2sdLfZqlxwdzyzeVC6Yy7wx8vYkqbsaxCq7BgcB58=; b=h0OC4Vt+XJYqkhFrHeE4/RyNyyj4Hu/asuNQEKXkuK8/VxCNVfjpvr/ZU+2GByPnbf59d2 rDPUvHNJsgtvj+Dvw9b3GjLwUkPv8LzcmkA57ryk2h/2SxyMSPwj3/2aJXY+cFGFeZvMlQ JenZQmsGHUtgHd0hEa6nFtZZIr1C+aU= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=LS+hNeQ4; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=khb2AjlS; dmarc=none; spf=pass (imf20.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668790983; a=rsa-sha256; cv=none; b=eR/9PA8N7k8W8jqutb0hx0boaJkBW6uiy+a1aCCmcfnIUWafK4ZFT+Q+FdQ6gcv+8D8W1Q W4FG31eQG0FqmtJpxDkOEySTwC6d5iwIqnQ9r/JJKp+FisKn1kmWDf55jrkFjRk7Ezodws mJsyG6eHBgle0MLw7Jdb/VeBEHiB+cM= X-Rspam-User: X-Stat-Signature: 3d3ajbj6tau3kst93w7k18f1ber4kdjy X-Rspamd-Queue-Id: 5C7A01C0028 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=LS+hNeQ4; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=khb2AjlS; dmarc=none; spf=pass (imf20.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Rspamd-Server: rspam07 X-HE-Tag: 1668790983-207732 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/16/22 11:26, David Hildenbrand wrote: > Let's catch abuse of FAULT_FLAG_WRITE early, such that we don't have to > care in all other handlers and might get "surprises" if we forget to do > so. > > Write faults without VM_MAYWRITE don't make any sense, and our > maybe_mkwrite() logic could have hidden such abuse for now. > > Write faults without VM_WRITE on something that is not a COW mapping is > similarly broken, and e.g., do_wp_page() could end up placing an > anonymous page into a shared mapping, which would be bad. > > This is a preparation for reliable R/O long-term pinning of pages in > private mappings, whereby we want to make sure that we will never break > COW in a read-only private mapping. > > Signed-off-by: David Hildenbrand Reviewed-by: Vlastimil Babka > --- > mm/memory.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index e014435a87db..c4fa378ec2a0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5170,6 +5170,14 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, > */ > if (!is_cow_mapping(vma->vm_flags)) > *flags &= ~FAULT_FLAG_UNSHARE; > + } else if (*flags & FAULT_FLAG_WRITE) { > + /* Write faults on read-only mappings are impossible ... */ > + if (WARN_ON_ONCE(!(vma->vm_flags & VM_MAYWRITE))) > + return VM_FAULT_SIGSEGV; > + /* ... and FOLL_FORCE only applies to COW mappings. */ > + if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE) && > + !is_cow_mapping(vma->vm_flags))) > + return VM_FAULT_SIGSEGV; > } > return 0; > }