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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 A59E2C83F14 for ; Tue, 29 Aug 2023 06:54:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693292041; h=from:from:sender: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:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=D7vi3BilGs8DUz3zPjvcFqHec3M+l9PIa7T3hGBDUC4=; b=bsJiRnZMvYlDtr0bRPD2HrJO2FkkATBsnN1oAIZsTn3Hl9v69vyKh8E4wze5Chx00gXK6t 1TG1aEyVh2QAOlciX7+tsQ7tBzxv3d9t2KBeJEKwzVFGZD6u3oL9jgdyaO8AteGj6fasLs 8uTene2YiOuhADW5U4Pb/jFyPwC75Fg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-139-C5AnpuKpP4-wp6hHOkz7iw-1; Tue, 29 Aug 2023 02:53:57 -0400 X-MC-Unique: C5AnpuKpP4-wp6hHOkz7iw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7EB51800193; Tue, 29 Aug 2023 06:53:55 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 946CE2166B29; Tue, 29 Aug 2023 06:53:53 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 768FB1946A41; Tue, 29 Aug 2023 06:53:52 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id BB3661946587 for ; Mon, 28 Aug 2023 14:27:47 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id 8C7A3140E964; Mon, 28 Aug 2023 14:27:47 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast09.extmail.prod.ext.rdu2.redhat.com [10.11.55.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 85538140E963 for ; Mon, 28 Aug 2023 14:27:47 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 264602A59569 for ; Mon, 28 Aug 2023 14:27:47 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-607-1KwS9UXIMaOYc6kK9t5bGg-1; Mon, 28 Aug 2023 10:27:42 -0400 X-MC-Unique: 1KwS9UXIMaOYc6kK9t5bGg-1 Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qadDM-009iIb-0l; Mon, 28 Aug 2023 14:27:36 +0000 Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 In-Reply-To: <20230826022852.GO3390869@ZenIV> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mailman-Approved-At: Tue, 29 Aug 2023 06:53:51 +0000 Subject: Re: [dm-devel] [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dave Kleikamp , jfs-discussion@lists.sourceforge.net, Jan Kara , "Darrick J. Wong" , linux-nvme@lists.infradead.org, Joseph Qi , dm-devel@redhat.com, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, Jack Wang , Alasdair Kergon , drbd-dev@lists.linbit.com, linux-s390@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, Sergey Senozhatsky , Christoph Hellwig , xen-devel@lists.xenproject.org, Gao Xiang , Christian Borntraeger , Kent Overstreet , Sven Schnelle , linux-pm@vger.kernel.org, Mike Snitzer , Chao Yu , Joern Engel , reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Christian Brauner , David Sterba , Jaegeuk Kim , Trond Myklebust , Jens Axboe , linux-raid@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, Ted Tso , linux-mm@kvack.org, Song Liu , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Minchan Kim , ocfs2-devel@oss.oracle.com, Anna Schumaker , linux-fsdevel@vger.kernel.org, "Md. Haris Iqbal" , Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: infradead.org Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel 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 08013C71153 for ; Mon, 28 Aug 2023 14:28:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230401AbjH1O2C (ORCPT ); Mon, 28 Aug 2023 10:28:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231778AbjH1O1n (ORCPT ); Mon, 28 Aug 2023 10:27:43 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90E6D9D; Mon, 28 Aug 2023 07:27:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=rbTi8dih1WwPPGr+ioF2zSIKKN 0mmMd7Mf6Y5CF6A3xbL6k1rG0Eq5PWNYD84YkTP/PYD6I8n7fwj9JtPf3x5xfflk7Of9PmT6yVoWg jDUfTlhnUqF1ibZ6C9C5Qp1FAcJBPSA1UYGVoKPgYhWBRS4hFyN/qulLfky0u5g5JfBjJuWo9rAVd OmVBPYeBaMmY44rW3+ehZ8vQr36snspggxlo5N+wQ2MnsZOlSw7LhANyJrm+6WDGYJ2q3IlcmhpsD alE6KXAxYfEVAogHtFQTNBnQoXb84wJ9x/IDWMwjf/34MizydIM1onWP9QQVyidEc4XNREZoED++f uj07NLVA==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qadDM-009iIb-0l; Mon, 28 Aug 2023 14:27:36 +0000 Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, Christoph Hellwig , Alasdair Kergon , Andrew Morton , Anna Schumaker , Chao Yu , Christian Borntraeger , "Darrick J. Wong" , Dave Kleikamp , David Sterba , dm-devel@redhat.com, drbd-dev@lists.linbit.com, Gao Xiang , Jack Wang , Jaegeuk Kim , jfs-discussion@lists.sourceforge.net, Joern Engel , Joseph Qi , Kent Overstreet , linux-bcache@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org, linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-nvme@lists.infradead.org, linux-pm@vger.kernel.org, linux-raid@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-xfs@vger.kernel.org, "Md. Haris Iqbal" , Mike Snitzer , Minchan Kim , ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, Sergey Senozhatsky , Song Liu , Sven Schnelle , target-devel@vger.kernel.org, Ted Tso , Trond Myklebust , xen-devel@lists.xenproject.org, Jens Axboe , Christian Brauner Subject: Re: [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 C97DEC83F15 for ; Mon, 28 Aug 2023 14:28:01 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=rbTi8dih; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4RZCZm1vPNz2yDD for ; Tue, 29 Aug 2023 00:28:00 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=rbTi8dih; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=bombadil.srs.infradead.org (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org; envelope-from=batv+b83d16e5cd0c301f07e4+7309+infradead.org+hch@bombadil.srs.infradead.org; receiver=lists.ozlabs.org) Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) (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 4RZCZf6X6Hz2yDD for ; Tue, 29 Aug 2023 00:27:54 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=rbTi8dih1WwPPGr+ioF2zSIKKN 0mmMd7Mf6Y5CF6A3xbL6k1rG0Eq5PWNYD84YkTP/PYD6I8n7fwj9JtPf3x5xfflk7Of9PmT6yVoWg jDUfTlhnUqF1ibZ6C9C5Qp1FAcJBPSA1UYGVoKPgYhWBRS4hFyN/qulLfky0u5g5JfBjJuWo9rAVd OmVBPYeBaMmY44rW3+ehZ8vQr36snspggxlo5N+wQ2MnsZOlSw7LhANyJrm+6WDGYJ2q3IlcmhpsD alE6KXAxYfEVAogHtFQTNBnQoXb84wJ9x/IDWMwjf/34MizydIM1onWP9QQVyidEc4XNREZoED++f uj07NLVA==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qadDM-009iIb-0l; Mon, 28 Aug 2023 14:27:36 +0000 Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Subject: Re: [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dave Kleikamp , jfs-discussion@lists.sourceforge.net, Jan Kara , "Darrick J. Wong" , linux-nvme@lists.infradead.org, Joseph Qi , dm-devel@redhat.com, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, Jack Wang , Alasdair Kergon , drbd-dev@lists.linbit.com, linux-s390@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, Sergey Senozhatsky , Christoph Hellwig , xen-devel@lists.xenproject.org, Christian Borntraeger , Kent Overstreet , Sven Schnelle , linux-pm@vger.kernel.org, Mike Snitzer , Joern Engel , reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Christian Brauner , David Sterba , Jaegeuk K im , Trond Myklebust , Jens Axboe , linux-raid@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, Ted Tso , linux-mm@kvack.org, Song Liu , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Minchan Kim , ocfs2-devel@oss.oracle.com, Anna Schumaker , linux-fsdevel@vger.kernel.org, "Md. Haris Iqbal" , Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. 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 lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (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 8866FC71153 for ; Mon, 28 Aug 2023 14:28:02 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1qadDm-0000Ud-BA; Mon, 28 Aug 2023 14:28:01 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qadDk-0000UJ-VC; Mon, 28 Aug 2023 14:27:59 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=OjNjhKiAIYuEv3WQ4yPGDDytOp 83ggWnUMHx5q5PUZDLCoRyqJILVRFTNoYH4BTmCXcBn2hJ4bkY2Y7+5t1WAZOSaCPrFmiuc8tIwAr Kv355kp1fFGJsgX+ueFPKW4RA4eB4m0r3o6y/8Jc2Xi+XpyqEQSAqbwcZm4J6mPh+9qk=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=igvQ4ZSXgmX4eRMDxizoJJARcx JffI3auEGlQqWfunpXYMWorI2BtPPwIHh1K//MUz9RABsytM+E39o652IrOThiFBlmRIVzxknSy1k nASYn6v4Hwoiqjvse64SVbSoY5ED5oz/7yXkkLcWAGGDEpiBeoAIAY7fzgfCDEiDhY/c=; Received: from bombadil.infradead.org ([198.137.202.133]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1qadDj-0005Cz-91; Mon, 28 Aug 2023 14:27:59 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=rbTi8dih1WwPPGr+ioF2zSIKKN 0mmMd7Mf6Y5CF6A3xbL6k1rG0Eq5PWNYD84YkTP/PYD6I8n7fwj9JtPf3x5xfflk7Of9PmT6yVoWg jDUfTlhnUqF1ibZ6C9C5Qp1FAcJBPSA1UYGVoKPgYhWBRS4hFyN/qulLfky0u5g5JfBjJuWo9rAVd OmVBPYeBaMmY44rW3+ehZ8vQr36snspggxlo5N+wQ2MnsZOlSw7LhANyJrm+6WDGYJ2q3IlcmhpsD alE6KXAxYfEVAogHtFQTNBnQoXb84wJ9x/IDWMwjf/34MizydIM1onWP9QQVyidEc4XNREZoED++f uj07NLVA==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qadDM-009iIb-0l; Mon, 28 Aug 2023 14:27:36 +0000 Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Headers-End: 1qadDj-0005Cz-91 Subject: Re: [f2fs-dev] [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dave Kleikamp , jfs-discussion@lists.sourceforge.net, Jan Kara , "Darrick J. Wong" , linux-nvme@lists.infradead.org, Joseph Qi , dm-devel@redhat.com, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, Jack Wang , Alasdair Kergon , drbd-dev@lists.linbit.com, linux-s390@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, Sergey Senozhatsky , Christoph Hellwig , xen-devel@lists.xenproject.org, Gao Xiang , Christian Borntraeger , Kent Overstreet , Sven Schnelle , linux-pm@vger.kernel.org, Mike Snitzer , Joern Engel , reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Christian Brauner , David Sterba , Jaegeuk Kim , Trond Myklebust , Jens Axboe , linux-raid@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, Ted Tso , linux-mm@kvack.org, Song Liu , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Minchan Kim , ocfs2-devel@oss.oracle.com, Anna Schumaker , linux-fsdevel@vger.kernel.org, "Md. Haris Iqbal" , Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle Date: Mon, 28 Aug 2023 07:27:36 -0700 Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uSnxqZdcrAYLPJPn0DfMY9X2iPdkTMayza8iox8Bem8=; b=rbTi8dih1WwPPGr+ioF2zSIKKN 0mmMd7Mf6Y5CF6A3xbL6k1rG0Eq5PWNYD84YkTP/PYD6I8n7fwj9JtPf3x5xfflk7Of9PmT6yVoWg jDUfTlhnUqF1ibZ6C9C5Qp1FAcJBPSA1UYGVoKPgYhWBRS4hFyN/qulLfky0u5g5JfBjJuWo9rAVd OmVBPYeBaMmY44rW3+ehZ8vQr36snspggxlo5N+wQ2MnsZOlSw7LhANyJrm+6WDGYJ2q3IlcmhpsD alE6KXAxYfEVAogHtFQTNBnQoXb84wJ9x/IDWMwjf/34MizydIM1onWP9QQVyidEc4XNREZoED++f uj07NLVA==; Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: drbd-dev-bounces-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org Errors-To: drbd-dev-bounces-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org To: Al Viro Cc: Dave Kleikamp , jfs-discussion-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Jan Kara , "Darrick J. Wong" , linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Joseph Qi , dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Jack Wang , Alasdair Kergon , drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org, linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Sergey Senozhatsky , Christoph Hellwig , xen-devel-GuqFBffKawtpuQazS67q72D2FQJk+8+b@public.gmane.org, Gao Xiang , Christian Borntraeger , Kent Overstreet , Sven Schnelle , linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mike Snitzer , Chao Yu , Joern Engel , re On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. 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 45A4EC71153 for ; Mon, 28 Aug 2023 14:27:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=hb7pazAH9l8ypeN0mZQv3R30XNcAOY7Yg/Po3wfITkc=; b=w734YshG8Krpu8 9gStaOL91I6y2l4t8G3qkIDgyWKcWiIB7mygbW9M6zTRajdTPX2Ahol1QtBfQFGBrE+pzL0D1uVDd c4rPAZE6SQbxGp6S0285ve9Mv3L1waAKI7IJWxCHZCQAfOaX5Atxo+ru7Oz4f0FziVK3Sg2SuZfI9 lt1knY0iKIVF5UDevg/XEk43BTuYHK6WZClH4WNEuVcITiiTRTd3+V74KFmB3GqV0fzSn2sGIZwZO YkT863Wkc5jUkRT12WdTMAVC/R6koqP2G4YH88FSpjWrwwYtUYq3rPKoXN+PhpCtDm9TkOOSmuhue KI6ZnEtOIQcTYvBUWP9w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qadDQ-009iJ3-0x; Mon, 28 Aug 2023 14:27:40 +0000 Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qadDM-009iIb-0l; Mon, 28 Aug 2023 14:27:36 +0000 Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, Christoph Hellwig , Alasdair Kergon , Andrew Morton , Anna Schumaker , Chao Yu , Christian Borntraeger , "Darrick J. Wong" , Dave Kleikamp , David Sterba , dm-devel@redhat.com, drbd-dev@lists.linbit.com, Gao Xiang , Jack Wang , Jaegeuk Kim , jfs-discussion@lists.sourceforge.net, Joern Engel , Joseph Qi , Kent Overstreet , linux-bcache@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org, linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-nvme@lists.infradead.org, linux-pm@vger.kernel.org, linux-raid@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-xfs@vger.kernel.org, "Md. Haris Iqbal" , Mike Snitzer , Minchan Kim , ocfs2-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, Sergey Senozhatsky , Song Liu , Sven Schnelle , target-devel@vger.kernel.org, Ted Tso , Trond Myklebust , xen-devel@lists.xenproject.org, Jens Axboe , Christian Brauner Subject: Re: [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually. ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/ From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by mail19.linbit.com (LINBIT Mail Daemon) with ESMTP id 6AFD64201C8 for ; Mon, 28 Aug 2023 16:27:46 +0200 (CEST) Date: Mon, 28 Aug 2023 07:27:36 -0700 From: Christoph Hellwig To: Al Viro Message-ID: References: <20230810171429.31759-1-jack@suse.cz> <20230825015843.GB95084@ZenIV> <20230825134756.o3wpq6bogndukn53@quack3> <20230826022852.GO3390869@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230826022852.GO3390869@ZenIV> Cc: Dave Kleikamp , jfs-discussion@lists.sourceforge.net, Jan Kara , "Darrick J. Wong" , linux-nvme@lists.infradead.org, Joseph Qi , dm-devel@redhat.com, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, Jack Wang , Alasdair Kergon , drbd-dev@lists.linbit.com, linux-s390@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, Sergey Senozhatsky , Christoph Hellwig , xen-devel@lists.xenproject.org, Gao Xiang , Christian Borntraeger , Kent Overstreet , Sven Schnelle , linux-pm@vger.kernel.org, Mike Snitzer , Chao Yu , Joern Engel , reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Christian Brauner , David Sterba , Jaegeuk Kim , Trond Myklebust , Jens Axboe , linux-raid@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, Ted Tso , linux-mm@kvack.org, Song Liu , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Minchan Kim , ocfs2-devel@oss.oracle.com, Anna Schumaker , linux-fsdevel@vger.kernel.org, "Md. Haris Iqbal" , Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Subject: Re: [Drbd-dev] [PATCH v2 0/29] block: Make blkdev_get_by_*() return handle List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, Aug 26, 2023 at 03:28:52AM +0100, Al Viro wrote: > I mean, look at claim_swapfile() for example: > p->bdev = blkdev_get_by_dev(inode->i_rdev, > FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); > if (IS_ERR(p->bdev)) { > error = PTR_ERR(p->bdev); > p->bdev = NULL; > return error; > } > p->old_block_size = block_size(p->bdev); > error = set_blocksize(p->bdev, PAGE_SIZE); > if (error < 0) > return error; > we already have the file opened, and we keep it opened all the way until > the swapoff(2); here we have noticed that it's a block device and we > * open the fucker again (by device number), this time claiming > it with our swap_info_struct as holder, to be closed at swapoff(2) time > (just before we close the file) Note that some drivers look at FMODE_EXCL/BLK_OPEN_EXCL in ->open. These are probably bogus and maybe we want to kill them, but that will need an audit first. > BTW, what happens if two threads call ioctl(fd, BLKBSZSET, &n) > for the same descriptor that happens to have been opened O_EXCL? > Without O_EXCL they would've been unable to claim the sucker at the same > time - the holder we are using is the address of a function argument, > i.e. something that points to kernel stack of the caller. Those would > conflict and we either get set_blocksize() calls fully serialized, or > one of the callers would eat -EBUSY. Not so in "opened with O_EXCL" > case - they can very well overlap and IIRC set_blocksize() does *not* > expect that kind of crap... It's all under CAP_SYS_ADMIN, so it's not > as if it was a meaningful security hole anyway, but it does look fishy. The user get to keep the pieces.. BLKBSZSET is kinda bogus anyway as the soft blocksize only matters for buffer_head-like I/O, and there only for file systems. Not idea why anyone would set it manually.