From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions Date: Fri, 12 Jul 2019 07:36:18 +0100 Message-ID: <20190712063617.GJ17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20190712041454.GG17978@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 , Andy Lutomirski , Christian Brauner , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Aleksa Sarai , Linus Torvalds , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org On Fri, Jul 12, 2019 at 05:14:54AM +0100, Al Viro wrote: > That's not quite guaranteed (it is possible to bind a symlink on top > of a regular file, and you will get LOOKUP_JUMPED on the entry into > trailing_symlink() when looking the result up). Moreover, why bother > with LOOKUP_JUMPED here? See that > nd->last_type = LAST_BIND; > several lines prior? That's precisely to be able to recognize those > suckers. ... except that this won't work these days (once upon a time it used to, but that had been a long time ago). However, that doesn't change the fact that the test is really wrong. So let's do it right: * set a new flag along with LOOKUP_JUMPED in nd_jump_link() * clear it in get_link() right before res = READ_ONCE(inode->i_link); * check it in trailing_symlink() (or callers thereof) The rest of comments stand, AFAICS. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:33532 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725562AbfGLGgu (ORCPT ); Fri, 12 Jul 2019 02:36:50 -0400 Date: Fri, 12 Jul 2019 07:36:18 +0100 From: Al Viro Subject: Re: [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions Message-ID: <20190712063617.GJ17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712041454.GG17978@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 , Andy Lutomirski , Christian Brauner , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Aleksa Sarai , Linus Torvalds , 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: <20190712063618.NDG-wQ-cByOheSporBxZHGmwQWhKLPiWniMyXjbW4es@z> On Fri, Jul 12, 2019 at 05:14:54AM +0100, Al Viro wrote: > That's not quite guaranteed (it is possible to bind a symlink on top > of a regular file, and you will get LOOKUP_JUMPED on the entry into > trailing_symlink() when looking the result up). Moreover, why bother > with LOOKUP_JUMPED here? See that > nd->last_type = LAST_BIND; > several lines prior? That's precisely to be able to recognize those > suckers. ... except that this won't work these days (once upon a time it used to, but that had been a long time ago). However, that doesn't change the fact that the test is really wrong. So let's do it right: * set a new flag along with LOOKUP_JUMPED in nd_jump_link() * clear it in get_link() right before res = READ_ONCE(inode->i_link); * check it in trailing_symlink() (or callers thereof) The rest of comments stand, AFAICS. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Date: Fri, 12 Jul 2019 06:36:18 +0000 Subject: Re: [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions Message-Id: <20190712063617.GJ17978@ZenIV.linux.org.uk> List-Id: References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> In-Reply-To: <20190712041454.GG17978@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 , Andy Lutomirski , Christian Brauner , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Aleksa Sarai , Linus Torvalds , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org On Fri, Jul 12, 2019 at 05:14:54AM +0100, Al Viro wrote: > That's not quite guaranteed (it is possible to bind a symlink on top > of a regular file, and you will get LOOKUP_JUMPED on the entry into > trailing_symlink() when looking the result up). Moreover, why bother > with LOOKUP_JUMPED here? See that > nd->last_type = LAST_BIND; > several lines prior? That's precisely to be able to recognize those > suckers. ... except that this won't work these days (once upon a time it used to, but that had been a long time ago). However, that doesn't change the fact that the test is really wrong. So let's do it right: * set a new flag along with LOOKUP_JUMPED in nd_jump_link() * clear it in get_link() right before res = READ_ONCE(inode->i_link); * check it in trailing_symlink() (or callers thereof) The rest of comments stand, AFAICS. 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 34456C742A8 for ; Fri, 12 Jul 2019 06:49:26 +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 BB9B020863 for ; Fri, 12 Jul 2019 06:49:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB9B020863 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 45lNnY6kxkzDqP0 for ; Fri, 12 Jul 2019 16:49:21 +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 45lNWF0KsmzDqf4 for ; Fri, 12 Jul 2019 16:36:54 +1000 (AEST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hlpAI-0006Xe-68; Fri, 12 Jul 2019 06:36:18 +0000 Date: Fri, 12 Jul 2019 07:36:18 +0100 From: Al Viro To: Aleksa Sarai Subject: Re: [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions Message-ID: <20190712063617.GJ17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712041454.GG17978@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 05:14:54AM +0100, Al Viro wrote: > That's not quite guaranteed (it is possible to bind a symlink on top > of a regular file, and you will get LOOKUP_JUMPED on the entry into > trailing_symlink() when looking the result up). Moreover, why bother > with LOOKUP_JUMPED here? See that > nd->last_type = LAST_BIND; > several lines prior? That's precisely to be able to recognize those > suckers. ... except that this won't work these days (once upon a time it used to, but that had been a long time ago). However, that doesn't change the fact that the test is really wrong. So let's do it right: * set a new flag along with LOOKUP_JUMPED in nd_jump_link() * clear it in get_link() right before res = READ_ONCE(inode->i_link); * check it in trailing_symlink() (or callers thereof) The rest of comments stand, AFAICS. 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 D96E0C742A8 for ; Fri, 12 Jul 2019 06:37:02 +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 AE18E208E4 for ; Fri, 12 Jul 2019 06:37:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="qUjwoUEH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE18E208E4 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=YHgT0muLXHMCTWW+R+p5lrujffdOgnMNss1eYkmf/cY=; b=qUjwoUEHAdS4Nq YDtakSPZAScPtSvTZsoOhgRLw+hYBTScoZXaPUEs1xnLks1aim841ADVsfCBdudtGG89OTP83Qlay 5ARt7d6SACV8KGvm1tMB3fNR9j/ux9/5I0ESb2yZXHOSBYT70OtbKUY+TSCncrZRCZnMjqdHXKxKP aUc6VzjtGifk+ZdXqKucOhfmaVhiQPpbyV9YX9SikY91rG/mtoYdQ8FTkMbvh4F3RAZP46w20ai7c 7jxN3Vab+L9uvRArxMGFH5D0zpgoAPMHAMOTaZBIqPkwB06tpcV9YahETOMMEyEwXMw6vsjO4TZic yg9NgF/X/xyX8H0zPt6g==; 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 1hlpAs-0001tj-CR; Fri, 12 Jul 2019 06:36:54 +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 1hlpAp-0001sn-Kz for linux-arm-kernel@lists.infradead.org; Fri, 12 Jul 2019 06:36:52 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hlpAI-0006Xe-68; Fri, 12 Jul 2019 06:36:18 +0000 Date: Fri, 12 Jul 2019 07:36:18 +0100 From: Al Viro To: Aleksa Sarai Subject: Re: [PATCH v9 01/10] namei: obey trailing magic-link DAC permissions Message-ID: <20190712063617.GJ17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190712041454.GG17978@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-20190711_233651_683928_FD86181F X-CRM114-Status: UNSURE ( 7.77 ) 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 05:14:54AM +0100, Al Viro wrote: > That's not quite guaranteed (it is possible to bind a symlink on top > of a regular file, and you will get LOOKUP_JUMPED on the entry into > trailing_symlink() when looking the result up). Moreover, why bother > with LOOKUP_JUMPED here? See that > nd->last_type = LAST_BIND; > several lines prior? That's precisely to be able to recognize those > suckers. ... except that this won't work these days (once upon a time it used to, but that had been a long time ago). However, that doesn't change the fact that the test is really wrong. So let's do it right: * set a new flag along with LOOKUP_JUMPED in nd_jump_link() * clear it in get_link() right before res = READ_ONCE(inode->i_link); * check it in trailing_symlink() (or callers thereof) The rest of comments stand, AFAICS. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel