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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 08141C43331 for ; Tue, 24 Mar 2020 13:15:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D2983208CA for ; Tue, 24 Mar 2020 13:15:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585055727; bh=GF0nQgHSqr93FGkRxyrNN14Mg7LyWH6kxP3Xm7fVJ30=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lKJikZp4Q5zw3bYXEA67e91JaIjrHs+qmuYkmrmgxsRWEf3L8+V4l2dSDejg/dNSq b2uTycPNjHG7wN92VurSf8sO3+JqQkPxn5Js5ioc6DcgWh41+F7pxkauktcAemzVia 4WEo+ZAcUCsxTl/2NHvuiwjEmQFaIK0DER4nR6D8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727778AbgCXNP0 (ORCPT ); Tue, 24 Mar 2020 09:15:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:34296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727743AbgCXNPY (ORCPT ); Tue, 24 Mar 2020 09:15:24 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1F103208CA; Tue, 24 Mar 2020 13:15:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585055723; bh=GF0nQgHSqr93FGkRxyrNN14Mg7LyWH6kxP3Xm7fVJ30=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CEBydxHpWfiR67T/Rgl/BuBETfTyI5n+tSiqycLjzYMH2qCyeaCf0uMnS2tongTnd RbzOHiU9GHr3YUFnuZnJDrX4zk6UzJjFMsu6vvu0E4VrH8CrV5dV2QXMFw/7WKy/8k K17pq+v4HI4mrS8752ZyhWIDcd3ULSJQwiglJy50= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, yangerkun , Jeff Layton , Sasha Levin Subject: [PATCH 5.4 001/102] locks: fix a potential use-after-free problem when wakeup a waiter Date: Tue, 24 Mar 2020 14:09:53 +0100 Message-Id: <20200324130806.654542883@linuxfoundation.org> X-Mailer: git-send-email 2.25.2 In-Reply-To: <20200324130806.544601211@linuxfoundation.org> References: <20200324130806.544601211@linuxfoundation.org> User-Agent: quilt/0.66 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: yangerkun [ Upstream commit 6d390e4b5d48ec03bb87e63cf0a2bff5f4e116da ] '16306a61d3b7 ("fs/locks: always delete_block after waiting.")' add the logic to check waiter->fl_blocker without blocked_lock_lock. And it will trigger a UAF when we try to wakeup some waiter： Thread 1 has create a write flock a on file, and now thread 2 try to unlock and delete flock a, thread 3 try to add flock b on the same file. Thread2 Thread3 flock syscall(create flock b) ...flock_lock_inode_wait flock_lock_inode(will insert our fl_blocked_member list to flock a's fl_blocked_requests) sleep flock syscall(unlock) ...flock_lock_inode_wait locks_delete_lock_ctx ...__locks_wake_up_blocks __locks_delete_blocks( b->fl_blocker = NULL) ... break by a signal locks_delete_block b->fl_blocker == NULL && list_empty(&b->fl_blocked_requests) success, return directly locks_free_lock b wake_up(&b->fl_waiter) trigger UAF Fix it by remove this logic, and this patch may also fix CVE-2019-19769. Cc: stable@vger.kernel.org Fixes: 16306a61d3b7 ("fs/locks: always delete_block after waiting.") Signed-off-by: yangerkun Signed-off-by: Jeff Layton Signed-off-by: Sasha Levin --- fs/locks.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index 44b6da0328426..426b55d333d5b 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -753,20 +753,6 @@ int locks_delete_block(struct file_lock *waiter) { int status = -ENOENT; - /* - * If fl_blocker is NULL, it won't be set again as this thread - * "owns" the lock and is the only one that might try to claim - * the lock. So it is safe to test fl_blocker locklessly. - * Also if fl_blocker is NULL, this waiter is not listed on - * fl_blocked_requests for some lock, so no other request can - * be added to the list of fl_blocked_requests for this - * request. So if fl_blocker is NULL, it is safe to - * locklessly check if fl_blocked_requests is empty. If both - * of these checks succeed, there is no need to take the lock. - */ - if (waiter->fl_blocker == NULL && - list_empty(&waiter->fl_blocked_requests)) - return status; spin_lock(&blocked_lock_lock); if (waiter->fl_blocker) status = 0; -- 2.20.1