From patchwork Tue Mar 15 12:08:50 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Tikhomirov X-Patchwork-Id: 8587561 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 12653C0553 for ; Tue, 15 Mar 2016 12:11:21 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 308B3202C8 for ; Tue, 15 Mar 2016 12:11:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2875520155 for ; Tue, 15 Mar 2016 12:11:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934659AbcCOMLS (ORCPT ); Tue, 15 Mar 2016 08:11:18 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:38979 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932688AbcCOMLQ (ORCPT ); Tue, 15 Mar 2016 08:11:16 -0400 Received: from dhcp-10-30-28-101.sw.ru ([10.30.16.121]) by relay.sw.ru (8.13.4/8.13.4) with ESMTP id u2FC8vOl001527; Tue, 15 Mar 2016 15:08:58 +0300 (MSK) From: Pavel Tikhomirov To: Seth Forshee , "Eric W. Biederman" , Cc: Serge Hallyn , Alexander Viro , Jeff Layton , "J. Bruce Fields" , Andy Lutomirski , linux-security-module@vger.kernel.org, linux-mtd@lists.infradead.org, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org, Pavel Tikhomirov , Konstantin Khorenko , Pavel Emelyanov Subject: [PATCH] fs: fix a posible leak of allocated superblock Date: Tue, 15 Mar 2016 15:08:50 +0300 Message-Id: <1458043730-14296-1-git-send-email-ptikhomirov@virtuozzo.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1443039368-55445-2-git-send-email-seth.forshee@canonical.com> References: <1443039368-55445-2-git-send-email-seth.forshee@canonical.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP We probably need to fix superblock leak in patch (v4 "fs: Add user namesapace member to struct super_block"): Imagine posible code path in sget_userns: we iterate through type->fs_supers and do not find suitable sb, we drop sb_lock to allocate s and go to retry. After we dropped sb_lock some other task from different userns takes sb_lock, it is already in retry stage and has s allocated, so it puts its s in type->fs_supers list. So in retry we will find these sb in list and check it has a different userns, and finally we will return without freeing s. Signed-off-by: Pavel Tikhomirov Acked-by: Seth Forshee --- fs/super.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/super.c b/fs/super.c index b4ee02b..24771b5 100644 --- a/fs/super.c +++ b/fs/super.c @@ -458,6 +458,10 @@ struct super_block *sget_userns(struct file_system_type *type, continue; if (user_ns != old->s_user_ns) { spin_unlock(&sb_lock); + if (s) { + up_write(&s->s_umount); + destroy_super(s); + } return ERR_PTR(-EBUSY); } if (!grab_super(old))