From patchwork Sat May 6 20:39:18 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 9715125 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 8354060352 for ; Sat, 6 May 2017 20:42:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 76E6F28346 for ; Sat, 6 May 2017 20:42:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6A32C28387; Sat, 6 May 2017 20:42:09 +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=unavailable 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 EF6B728346 for ; Sat, 6 May 2017 20:42:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754164AbdEFUjo (ORCPT ); Sat, 6 May 2017 16:39:44 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:37644 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753442AbdEFUjj (ORCPT ); Sat, 6 May 2017 16:39:39 -0400 Received: from localhost (unknown [104.129.198.110]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 475619FA; Sat, 6 May 2017 20:39:38 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitry Vyukov , Thomas Gleixner , syzkaller , Al Viro , linux-fsdevel@vger.kernel.org Subject: [PATCH 4.10 1/5] timerfd: Protect the might cancel mechanism proper Date: Sat, 6 May 2017 13:39:18 -0700 Message-Id: <20170506203843.462281343@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170506203843.407624742@linuxfoundation.org> References: <20170506203843.407624742@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 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 4.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 1e38da300e1e395a15048b0af1e5305bd91402f6 upstream. The handling of the might_cancel queueing is not properly protected, so parallel operations on the file descriptor can race with each other and lead to list corruptions or use after free. Protect the context for these operations with a seperate lock. The wait queue lock cannot be reused for this because that would create a lock inversion scenario vs. the cancel lock. Replacing might_cancel with an atomic (atomic_t or atomic bit) does not help either because it still can race vs. the actual list operation. Reported-by: Dmitry Vyukov Signed-off-by: Thomas Gleixner Cc: "linux-fsdevel@vger.kernel.org" Cc: syzkaller Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701311521430.3457@nanos Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- fs/timerfd.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) --- a/fs/timerfd.c +++ b/fs/timerfd.c @@ -40,6 +40,7 @@ struct timerfd_ctx { short unsigned settime_flags; /* to show in fdinfo */ struct rcu_head rcu; struct list_head clist; + spinlock_t cancel_lock; bool might_cancel; }; @@ -112,7 +113,7 @@ void timerfd_clock_was_set(void) rcu_read_unlock(); } -static void timerfd_remove_cancel(struct timerfd_ctx *ctx) +static void __timerfd_remove_cancel(struct timerfd_ctx *ctx) { if (ctx->might_cancel) { ctx->might_cancel = false; @@ -122,6 +123,13 @@ static void timerfd_remove_cancel(struct } } +static void timerfd_remove_cancel(struct timerfd_ctx *ctx) +{ + spin_lock(&ctx->cancel_lock); + __timerfd_remove_cancel(ctx); + spin_unlock(&ctx->cancel_lock); +} + static bool timerfd_canceled(struct timerfd_ctx *ctx) { if (!ctx->might_cancel || ctx->moffs != KTIME_MAX) @@ -132,6 +140,7 @@ static bool timerfd_canceled(struct time static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags) { + spin_lock(&ctx->cancel_lock); if ((ctx->clockid == CLOCK_REALTIME || ctx->clockid == CLOCK_REALTIME_ALARM) && (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) { @@ -141,9 +150,10 @@ static void timerfd_setup_cancel(struct list_add_rcu(&ctx->clist, &cancel_list); spin_unlock(&cancel_lock); } - } else if (ctx->might_cancel) { - timerfd_remove_cancel(ctx); + } else { + __timerfd_remove_cancel(ctx); } + spin_unlock(&ctx->cancel_lock); } static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) @@ -400,6 +410,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clo return -ENOMEM; init_waitqueue_head(&ctx->wqh); + spin_lock_init(&ctx->cancel_lock); ctx->clockid = clockid; if (isalarm(ctx))