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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 3F598C433DF for ; Thu, 20 Aug 2020 16:56:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 256D3207DE for ; Thu, 20 Aug 2020 16:56:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730130AbgHTQ4Q (ORCPT ); Thu, 20 Aug 2020 12:56:16 -0400 Received: from alexa-out.qualcomm.com ([129.46.98.28]:7416 "EHLO alexa-out.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729223AbgHTQ4O (ORCPT ); Thu, 20 Aug 2020 12:56:14 -0400 Received: from ironmsg07-lv.qualcomm.com (HELO ironmsg07-lv.qulacomm.com) ([10.47.202.151]) by alexa-out.qualcomm.com with ESMTP; 20 Aug 2020 09:56:12 -0700 Received: from ironmsg01-blr.qualcomm.com ([10.86.208.130]) by ironmsg07-lv.qulacomm.com with ESMTP/TLS/AES256-SHA; 20 Aug 2020 09:56:11 -0700 Received: from c-ppvk-linux.qualcomm.com ([10.206.24.34]) by ironmsg01-blr.qualcomm.com with ESMTP; 20 Aug 2020 22:26:01 +0530 Received: by c-ppvk-linux.qualcomm.com (Postfix, from userid 2304101) id 0A35A51FB; Thu, 20 Aug 2020 22:25:58 +0530 (IST) From: Pradeep P V K To: miklos@szeredi.hu, linux-fsdevel@vger.kernel.org Cc: stummala@codeaurora.org, sayalil@codeaurora.org, Pradeep P V K Subject: [PATCH V1] fuse: Fix VM_BUG_ON_PAGE issue while accessing zero ref count page Date: Thu, 20 Aug 2020 22:25:55 +0530 Message-Id: <1597942555-904-1-git-send-email-ppvk@codeaurora.org> X-Mailer: git-send-email 1.9.1 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org There is a potential race between fuse_abort_conn() and fuse_copy_page() as shown below, due to which VM_BUG_ON_PAGE crash is observed. context#1: context#2: fuse_dev_do_read() fuse_abort_conn() ->fuse_copy_args() ->end_requests() ->fuse_copy_pages() ->request_end() ->fuse_copy_page() ->fuse_writepage_end) ->fuse_ref_page() ->fuse_writepage_free() ->__free_page() ->put_page_testzero() ->get_page() ->VM_BUG_ON_PAGE() This results in below crash as when ->put_page_testzero() in context#2 decrease the page reference and get_page() in context#1 accessed it with zero page reference count. [ 174.391095] (1)[10406:Thread-6]page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u)) [ 174.391113] (1)[10406:Thread-6]page allocated via order 0, migratetype Unmovable, gfp_mask 0x620042(GFP_NOFS|__GFP_HIGHMEM|__GFP_HARDWALL), pid 261, ts 174390946312 ns [ 174.391135] (1)[10406:Thread-6] prep_new_page+0x13c/0x210 [ 174.391148] (1)[10406:Thread-6] get_page_from_freelist+0x21ac/0x2370 [ 174.391161] (1)[10406:Thread-6] __alloc_pages_nodemask+0x244/0x14a8 [ 174.391176] (1)[10406:Thread-6] fuse_writepages_fill+0x150/0x708 [ 174.391190] (1)[10406:Thread-6] write_cache_pages+0x3d8/0x550 [ 174.391202] (1)[10406:Thread-6] fuse_writepages+0x94/0x130 [ 174.391214] (1)[10406:Thread-6] do_writepages+0x74/0x140 [ 174.391228] (1)[10406:Thread-6] __writeback_single_inode+0x168/0x788 [ 174.391239] (1)[10406:Thread-6] writeback_sb_inodes+0x56c/0xab8 [ 174.391251] (1)[10406:Thread-6] __writeback_inodes_wb+0x94/0x180 [ 174.391262] (1)[10406:Thread-6] wb_writeback+0x318/0x618 [ 174.391274] (1)[10406:Thread-6] wb_workfn+0x468/0x828 [ 174.391290] (1)[10406:Thread-6] process_one_work+0x3d0/0x720 [ 174.391302] (1)[10406:Thread-6] worker_thread+0x234/0x4c0 [ 174.391314] (1)[10406:Thread-6] kthread+0x144/0x158 [ 174.391327] (1)[10406:Thread-6] ret_from_fork+0x10/0x1c [ 174.391363] (1)[10406:Thread-6]------------[ cut here ]------------ [ 174.391371] (1)[10406:Thread-6]kernel BUG at include/linux/mm.h:980! [ 174.391381] (1)[10406:Thread-6]Internal error: Oops - BUG: 0 [#1] ... [ 174.486928] (1)[10406:Thread-6]pc : fuse_copy_page+0x750/0x790 [ 174.493029] (1)[10406:Thread-6]lr : fuse_copy_page+0x750/0x790 [ 174.718831] (1)[10406:Thread-6] fuse_copy_page+0x750/0x790 [ 174.718838] (1)[10406:Thread-6] fuse_copy_args+0xb4/0x1e8 [ 174.718843] (1)[10406:Thread-6] fuse_dev_do_read+0x424/0x888 [ 174.718848] (1)[10406:Thread-6] fuse_dev_splice_read+0x94/0x200 [ 174.718856] (1)[10406:Thread-6] __arm64_sys_splice+0x874/0xb20 [ 174.718864] (1)[10406:Thread-6] el0_svc_common+0xc8/0x240 [ 174.718869] (1)[10406:Thread-6] el0_svc_handler+0x6c/0x88 [ 174.718875] (1)[10406:Thread-6] el0_svc+0x8/0xc [ 174.778853] (1)[10406:Thread-6]Kernel panic - not syncing: Fatal Fix this by protecting fuse_copy_pages() with fc->lock. Signed-off-by: Pradeep P V K --- fs/fuse/dev.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 02b3c36..ca4f63c 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -948,22 +948,26 @@ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes, int zeroing) { unsigned i; + int err = 0; struct fuse_req *req = cs->req; struct fuse_args_pages *ap = container_of(req->args, typeof(*ap), args); - + if (req->ff) + spin_lock(&req->ff->fc->lock); for (i = 0; i < ap->num_pages && (nbytes || zeroing); i++) { - int err; unsigned int offset = ap->descs[i].offset; unsigned int count = min(nbytes, ap->descs[i].length); err = fuse_copy_page(cs, &ap->pages[i], offset, count, zeroing); if (err) - return err; + goto err; nbytes -= count; } - return 0; +err: + if (req->ff) + spin_unlock(&req->ff->fc->lock); + return err; } /* Copy a single argument in the request to/from userspace buffer */ -- 1.9.1