From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Date: Sat, 13 Jul 2019 03:41:53 +0100 Message-ID: <20190713024153.GA3817@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20190712150026.GO17978@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Aleksa Sarai Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > > if (flags & LOOKUP_BENEATH) { > > nd->root = nd->path; > > if (!(flags & LOOKUP_RCU)) > > path_get(&nd->root); > > else > > nd->root_seq = nd->seq; > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > you are pretty much guaranteed that lazy pathwalk will fail, > when it comes to complete_walk(). > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > combination would someday get passed? I don't understand what's going on with ->r_seq in there - your call of path_is_under() is after having (re-)sampled rename_lock, but if that was the only .. in there, who's going to recheck the value? For that matter, what's to guarantee that the thing won't get moved just as you are returning from handle_dots()? IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:48010 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727338AbfGMCmU (ORCPT ); Fri, 12 Jul 2019 22:42:20 -0400 Date: Sat, 13 Jul 2019 03:41:53 +0100 From: Al Viro Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-ID: <20190713024153.GA3817@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712150026.GO17978@ZenIV.linux.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Aleksa Sarai Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org Message-ID: <20190713024153.PEj5iXOW--bwyd91k08wWXjUS1QD6XMk4RYA_cfVo2M@z> On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > > if (flags & LOOKUP_BENEATH) { > > nd->root = nd->path; > > if (!(flags & LOOKUP_RCU)) > > path_get(&nd->root); > > else > > nd->root_seq = nd->seq; > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > you are pretty much guaranteed that lazy pathwalk will fail, > when it comes to complete_walk(). > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > combination would someday get passed? I don't understand what's going on with ->r_seq in there - your call of path_is_under() is after having (re-)sampled rename_lock, but if that was the only .. in there, who's going to recheck the value? For that matter, what's to guarantee that the thing won't get moved just as you are returning from handle_dots()? IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Date: Sat, 13 Jul 2019 02:41:53 +0000 Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-Id: <20190713024153.GA3817@ZenIV.linux.org.uk> List-Id: References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> In-Reply-To: <20190712150026.GO17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Aleksa Sarai Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > > if (flags & LOOKUP_BENEATH) { > > nd->root = nd->path; > > if (!(flags & LOOKUP_RCU)) > > path_get(&nd->root); > > else > > nd->root_seq = nd->seq; > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > you are pretty much guaranteed that lazy pathwalk will fail, > when it comes to complete_walk(). > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > combination would someday get passed? I don't understand what's going on with ->r_seq in there - your call of path_is_under() is after having (re-)sampled rename_lock, but if that was the only .. in there, who's going to recheck the value? For that matter, what's to guarantee that the thing won't get moved just as you are returning from handle_dots()? IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? 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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B8DFC742D2 for ; Sat, 13 Jul 2019 02:44:27 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D4719208E4 for ; Sat, 13 Jul 2019 02:44:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D4719208E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45lvJS2zPrzDqBP for ; Sat, 13 Jul 2019 12:44:24 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=ftp.linux.org.uk (client-ip=195.92.253.2; helo=zeniv.linux.org.uk; envelope-from=viro@ftp.linux.org.uk; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [195.92.253.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45lvGL4jSmzDqg3 for ; Sat, 13 Jul 2019 12:42:31 +1000 (AEST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hm7yz-0001A3-CY; Sat, 13 Jul 2019 02:41:53 +0000 Date: Sat, 13 Jul 2019 03:41:53 +0100 From: Al Viro To: Aleksa Sarai Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-ID: <20190713024153.GA3817@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712150026.GO17978@ZenIV.linux.org.uk> User-Agent: Mutt/1.11.3 (2019-02-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Alexei Starovoitov , linux-kernel@vger.kernel.org, David Howells , linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Shuah Khan , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen , Aleksa Sarai , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook , Arnd Bergmann , Jann Horn , linuxppc-dev@lists.ozlabs.org, linux-m68k@lists.linux-m68k.org, Andy Lutomirski , Shuah Khan , David Drysdale , Christian Brauner , "J. Bruce Fields" , linux-parisc@vger.kernel.org, linux-api@vger.kernel.org, Chanho Min , Jeff Layton , Oleg Nesterov , Eric Biederman , linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > > if (flags & LOOKUP_BENEATH) { > > nd->root = nd->path; > > if (!(flags & LOOKUP_RCU)) > > path_get(&nd->root); > > else > > nd->root_seq = nd->seq; > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > you are pretty much guaranteed that lazy pathwalk will fail, > when it comes to complete_walk(). > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > combination would someday get passed? I don't understand what's going on with ->r_seq in there - your call of path_is_under() is after having (re-)sampled rename_lock, but if that was the only .. in there, who's going to recheck the value? For that matter, what's to guarantee that the thing won't get moved just as you are returning from handle_dots()? IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? 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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A08A9C742D7 for ; Sat, 13 Jul 2019 02:42:36 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 6F962208E4 for ; Sat, 13 Jul 2019 02:42:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ezgIX99b" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F962208E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=qRxUMxv5n9bSA/iaJJPBjic6Xtvzf1weCuou0M50cR4=; b=ezgIX99bR+/qCY 7BZrUO/QeaV1n34BKtcA1c1eMnIhqiVBnrroTpn6HCrD3LYJHOvkQuiGvi3C37PSgi5it8doBaFrE EhI9d08Ehfk4FBQ/shjhfEk2OEXoBgOX0gjaSVm2hoRb7+Qn3UFJQoWHV9F+jBtwygmEmCx8/BWMG gwtcJd+8u/iQdsagwIJIUrkwgv1t+aF5q5yIciP42MG6MbN1bbSuf1zTJ+LEjXVkut4jqOrEFDYTE Q64RQ1Kb0G/p1D+ufnWpLwLGqcDsc8g3REgYzHXHAeWFjaiAbff4gKvjT+0pnd3BUHwVUaNlTLSUd DSHlG5jN9jBsnZOERZHw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hm7zY-0006Wc-S0; Sat, 13 Jul 2019 02:42:28 +0000 Received: from zeniv.linux.org.uk ([195.92.253.2]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hm7zT-0006W8-JU for linux-arm-kernel@lists.infradead.org; Sat, 13 Jul 2019 02:42:25 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hm7yz-0001A3-CY; Sat, 13 Jul 2019 02:41:53 +0000 Date: Sat, 13 Jul 2019 03:41:53 +0100 From: Al Viro To: Aleksa Sarai Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-ID: <20190713024153.GA3817@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190712150026.GO17978@ZenIV.linux.org.uk> User-Agent: Mutt/1.11.3 (2019-02-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190712_194223_899018_D53C8A82 X-CRM114-Status: UNSURE ( 9.67 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Alexei Starovoitov , linux-kernel@vger.kernel.org, David Howells , linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Shuah Khan , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen , Aleksa Sarai , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook , Arnd Bergmann , Jann Horn , linuxppc-dev@lists.ozlabs.org, linux-m68k@lists.linux-m68k.org, Andy Lutomirski , Shuah Khan , David Drysdale , Christian Brauner , "J. Bruce Fields" , linux-parisc@vger.kernel.org, linux-api@vger.kernel.org, Chanho Min , Jeff Layton , Oleg Nesterov , Eric Biederman , linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > > if (flags & LOOKUP_BENEATH) { > > nd->root = nd->path; > > if (!(flags & LOOKUP_RCU)) > > path_get(&nd->root); > > else > > nd->root_seq = nd->seq; > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > you are pretty much guaranteed that lazy pathwalk will fail, > when it comes to complete_walk(). > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > combination would someday get passed? I don't understand what's going on with ->r_seq in there - your call of path_is_under() is after having (re-)sampled rename_lock, but if that was the only .. in there, who's going to recheck the value? For that matter, what's to guarantee that the thing won't get moved just as you are returning from handle_dots()? IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel