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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 715FFC43603 for ; Mon, 5 Apr 2021 09:05:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50318613A3 for ; Mon, 5 Apr 2021 09:05:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238117AbhDEJE0 (ORCPT ); Mon, 5 Apr 2021 05:04:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:46030 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237596AbhDEJDO (ORCPT ); Mon, 5 Apr 2021 05:03:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CC0B861002; Mon, 5 Apr 2021 09:03:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1617613387; bh=QHdcJTezi9bvA14StpNy4bsRWJsJICWDl/4yxaAs0+Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UO5y6SC5ui5r6TxI2ntA+Bg9yfJ57D9rVZOgv1PtOPNcBkDoHEy0mLOhXpRunPH26 3gWL9G8DEf90B/BO/y9p01i3iNfY2JbiAe9d+Fi2ni63SP/AzuWoIKHLwMfriX952V /vaK1tqnUwiW9EgjkJbe3IDUJ+zPKwNdgMBT7RuY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ritesh Harjani , "Darrick J. Wong" , Christoph Hellwig , Sasha Levin Subject: [PATCH 5.4 10/74] iomap: Fix negative assignment to unsigned sis->pages in iomap_swapfile_activate Date: Mon, 5 Apr 2021 10:53:34 +0200 Message-Id: <20210405085025.065661001@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210405085024.703004126@linuxfoundation.org> References: <20210405085024.703004126@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ritesh Harjani [ Upstream commit 5808fecc572391867fcd929662b29c12e6d08d81 ] In case if isi.nr_pages is 0, we are making sis->pages (which is unsigned int) a huge value in iomap_swapfile_activate() by assigning -1. This could cause a kernel crash in kernel v4.18 (with below signature). Or could lead to unknown issues on latest kernel if the fake big swap gets used. Fix this issue by returning -EINVAL in case of nr_pages is 0, since it is anyway a invalid swapfile. Looks like this issue will be hit when we have pagesize < blocksize type of configuration. I was able to hit the issue in case of a tiny swap file with below test script. https://raw.githubusercontent.com/riteshharjani/LinuxStudy/master/scripts/swap-issue.sh kernel crash analysis on v4.18 ============================== On v4.18 kernel, it causes a kernel panic, since sis->pages becomes a huge value and isi.nr_extents is 0. When 0 is returned it is considered as a swapfile over NFS and SWP_FILE is set (sis->flags |= SWP_FILE). Then when swapoff was getting called it was calling a_ops->swap_deactivate() if (sis->flags & SWP_FILE) is true. Since a_ops->swap_deactivate() is NULL in case of XFS, it causes below panic. Panic signature on v4.18 kernel: ======================================= root@qemu:/home/qemu# [ 8291.723351] XFS (loop2): Unmounting Filesystem [ 8292.123104] XFS (loop2): Mounting V5 Filesystem [ 8292.132451] XFS (loop2): Ending clean mount [ 8292.263362] Adding 4294967232k swap on /mnt1/test/swapfile. Priority:-2 extents:1 across:274877906880k [ 8292.277834] Unable to handle kernel paging request for instruction fetch [ 8292.278677] Faulting instruction address: 0x00000000 cpu 0x19: Vector: 400 (Instruction Access) at [c0000009dd5b7ad0] pc: 0000000000000000 lr: c0000000003eb9dc: destroy_swap_extents+0xfc/0x120 sp: c0000009dd5b7d50 msr: 8000000040009033 current = 0xc0000009b6710080 paca = 0xc00000003ffcb280 irqmask: 0x03 irq_happened: 0x01 pid = 5604, comm = swapoff Linux version 4.18.0 (riteshh@xxxxxxx) (gcc version 8.4.0 (Ubuntu 8.4.0-1ubuntu1~18.04)) #57 SMP Wed Mar 3 01:33:04 CST 2021 enter ? for help [link register ] c0000000003eb9dc destroy_swap_extents+0xfc/0x120 [c0000009dd5b7d50] c0000000025a7058 proc_poll_event+0x0/0x4 (unreliable) [c0000009dd5b7da0] c0000000003f0498 sys_swapoff+0x3f8/0x910 [c0000009dd5b7e30] c00000000000bbe4 system_call+0x5c/0x70 Exception: c01 (System Call) at 00007ffff7d208d8 Signed-off-by: Ritesh Harjani [djwong: rework the comment to provide more details] Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Signed-off-by: Sasha Levin --- fs/iomap/swapfile.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c index 152a230f668d..bd0cc3dcc980 100644 --- a/fs/iomap/swapfile.c +++ b/fs/iomap/swapfile.c @@ -169,6 +169,16 @@ int iomap_swapfile_activate(struct swap_info_struct *sis, return ret; } + /* + * If this swapfile doesn't contain even a single page-aligned + * contiguous range of blocks, reject this useless swapfile to + * prevent confusion later on. + */ + if (isi.nr_pages == 0) { + pr_warn("swapon: Cannot find a single usable page in file.\n"); + return -EINVAL; + } + *pagespan = 1 + isi.highest_ppage - isi.lowest_ppage; sis->max = isi.nr_pages; sis->pages = isi.nr_pages - 1; -- 2.30.1