From patchwork Wed Oct 11 15:10:52 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eryu Guan X-Patchwork-Id: 9999887 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2296760244 for ; Wed, 11 Oct 2017 15:11:43 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0CD3528A56 for ; Wed, 11 Oct 2017 15:11:43 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 01B8028A66; Wed, 11 Oct 2017 15:11:42 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A03EE28A56 for ; Wed, 11 Oct 2017 15:11:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752035AbdJKPLl (ORCPT ); Wed, 11 Oct 2017 11:11:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50894 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751895AbdJKPLk (ORCPT ); Wed, 11 Oct 2017 11:11:40 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1398F7EAA2; Wed, 11 Oct 2017 15:11:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 1398F7EAA2 Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=eguan@redhat.com Received: from localhost (dhcp-12-147.nay.redhat.com [10.66.12.147]) by smtp.corp.redhat.com (Postfix) with ESMTP id 809A16C400; Wed, 11 Oct 2017 15:11:35 +0000 (UTC) From: Eryu Guan To: linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org Cc: Alexander Viro , Eryu Guan , Oleg Nesterov Subject: [PATCH v2] binfmt_misc: Node could be NULL when evicting inode Date: Wed, 11 Oct 2017 23:10:52 +0800 Message-Id: <20171011151052.14381-1-eguan@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 11 Oct 2017 15:11:40 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP inode->i_private is assigned by a Node pointer only after registering a new binary format, and it's possible to be NULL if inode was created by bm_fill_super() (or iput() was called by the error path in bm_register_write()), and this could result in NULL pointer dereference when evicting such an inode. e.g. mount binfmt_misc filesystem then umount it immediately: mount -t binfmt_misc binfmt_misc /proc/sys/fs/binfmt_misc umount /proc/sys/fs/binfmt_misc [ 9379.678259] BUG: unable to handle kernel NULL pointer dereference at 0000000000000013 [ 9379.985952] IP: bm_evict_inode+0x16/0x40 [binfmt_misc] ... [ 9380.964911] Call Trace: [ 9380.977633] evict+0xd3/0x1a0 [ 9380.994449] iput+0x17d/0x1d0 [ 9381.010306] dentry_unlink_inode+0xb9/0xf0 [ 9381.034046] __dentry_kill+0xc7/0x170 [ 9381.055145] shrink_dentry_list+0x122/0x280 [ 9381.078908] shrink_dcache_parent+0x39/0x90 [ 9381.103082] do_one_tree+0x12/0x40 [ 9381.122005] shrink_dcache_for_umount+0x2d/0x90 [ 9381.146517] generic_shutdown_super+0x1f/0x120 [ 9381.171644] kill_litter_super+0x29/0x40 [ 9381.193513] deactivate_locked_super+0x43/0x70 [ 9381.219177] deactivate_super+0x45/0x60 [ 9381.240130] cleanup_mnt+0x3f/0x70 [ 9381.259064] __cleanup_mnt+0x12/0x20 [ 9381.279802] task_work_run+0x86/0xa0 [ 9381.299612] exit_to_usermode_loop+0x6d/0x99 [ 9381.323872] syscall_return_slowpath+0xba/0xf0 [ 9381.350464] entry_SYSCALL_64_fastpath+0xa3/0xa Fix it by making sure Node (e) is not NULL. Cc: Oleg Nesterov Fixes: 83f918274e4b ("exec: binfmt_misc: shift filp_close(interp_file) from kill_node() to bm_evict_inode()") Acked-by: Oleg Nesterov Signed-off-by: Eryu Guan --- v2: - update commit log as suggested by Oleg Hi Andrew, could you please help replace the v1 patch in -mm tree with this v2? The new commit log describes the problem more accurately. Thanks! fs/binfmt_misc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index 2a46762def31..a7c5a9861bef 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -596,7 +596,7 @@ static void bm_evict_inode(struct inode *inode) { Node *e = inode->i_private; - if (e->flags & MISC_FMT_OPEN_FILE) + if (e && e->flags & MISC_FMT_OPEN_FILE) filp_close(e->interp_file, NULL); clear_inode(inode);