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=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 75FD9C433E2 for ; Thu, 25 Mar 2021 11:29:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F81C61A40 for ; Thu, 25 Mar 2021 11:29:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231360AbhCYL3V (ORCPT ); Thu, 25 Mar 2021 07:29:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:35170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230478AbhCYL0Q (ORCPT ); Thu, 25 Mar 2021 07:26:16 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CE5C361A4C; Thu, 25 Mar 2021 11:26:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616671570; bh=RAcmr8XK87Ey3UEhsWQklDNIkjlPCFA2XTgbM233wvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SZQWtYrbpm6jfSJQOQgcbP6OCvWT11Ubd8ymjejPCRYxsteLYYVTOu8yjnvzcne8t NdoScHPMoHXZ5SMjYwSnUFQZWtHWTlUQzsiUkXOAj+byastUEwP2XZfmFv3r9+nrwZ egWFYuAFBcMGSu3YX3213x6gor0iXgEUlx2Oif5Pl8T96tciGzXuGQl7x7sUMG15SM Sf0CvHA9eovNxSOKff1aDY/qJRdytAooI34PQuPZbsH6ix/MBIne42d213rlqAARU3 eVC3Cj7SSl2YO+Z6WZJ+V+IOHQTvkyV0P7iYwqYqgchQAG0QNF2JXllubCcOcHRS9K HEnQGkff0wBJA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ritesh Harjani , "Darrick J . Wong" , Christoph Hellwig , Sasha Levin , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 08/39] iomap: Fix negative assignment to unsigned sis->pages in iomap_swapfile_activate Date: Thu, 25 Mar 2021 07:25:27 -0400 Message-Id: <20210325112558.1927423-8-sashal@kernel.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210325112558.1927423-1-sashal@kernel.org> References: <20210325112558.1927423-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 a648dbf6991e..a5e478de1417 100644 --- a/fs/iomap/swapfile.c +++ b/fs/iomap/swapfile.c @@ -170,6 +170,16 @@ 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