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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5195C32772 for ; Tue, 23 Aug 2022 08:30:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243814AbiHWIaC (ORCPT ); Tue, 23 Aug 2022 04:30:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244257AbiHWI0b (ORCPT ); Tue, 23 Aug 2022 04:26:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4B2C173921; Tue, 23 Aug 2022 01:14:25 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 24A016129A; Tue, 23 Aug 2022 08:14:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30644C433C1; Tue, 23 Aug 2022 08:14:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661242462; bh=w/ws2DL+rOAPKGt41HhTtwj8mh2+FQSFUgu3NzsRKgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kEadTVknMWwBbQ1z6SmS9/MUcrCyn/so+gazDohkZyumaK9D0nPKatmpABE+zgwV/ aZPZCMC0LWm3ZajY8pH1HIsa3+hRB1T/g7P1y2R4tCjRLO5BQqX5GnE4D6ddkCH1GQ kCHb44TRguP2n9zYLvBBpvgFUE1fL/JERxu59YFM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefano Garzarella , Peilin Ye , "David S. Miller" , syzbot+b03f55bf128f9a38f064@syzkaller.appspotmail.com Subject: [PATCH 4.9 075/101] vsock: Fix memory leak in vsock_connect() Date: Tue, 23 Aug 2022 10:03:48 +0200 Message-Id: <20220823080037.435200290@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080034.579196046@linuxfoundation.org> References: <20220823080034.579196046@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peilin Ye commit 7e97cfed9929eaabc41829c395eb0d1350fccb9d upstream. An O_NONBLOCK vsock_connect() request may try to reschedule @connect_work. Imagine the following sequence of vsock_connect() requests: 1. The 1st, non-blocking request schedules @connect_work, which will expire after 200 jiffies. Socket state is now SS_CONNECTING; 2. Later, the 2nd, blocking request gets interrupted by a signal after a few jiffies while waiting for the connection to be established. Socket state is back to SS_UNCONNECTED, but @connect_work is still pending, and will expire after 100 jiffies. 3. Now, the 3rd, non-blocking request tries to schedule @connect_work again. Since @connect_work is already scheduled, schedule_delayed_work() silently returns. sock_hold() is called twice, but sock_put() will only be called once in vsock_connect_timeout(), causing a memory leak reported by syzbot: BUG: memory leak unreferenced object 0xffff88810ea56a40 (size 1232): comm "syz-executor756", pid 3604, jiffies 4294947681 (age 12.350s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 28 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 (..@............ backtrace: [] sk_prot_alloc+0x3e/0x1b0 net/core/sock.c:1930 [] sk_alloc+0x32/0x2e0 net/core/sock.c:1989 [] __vsock_create.constprop.0+0x38/0x320 net/vmw_vsock/af_vsock.c:734 [] vsock_create+0xc1/0x2d0 net/vmw_vsock/af_vsock.c:2203 [] __sock_create+0x1ab/0x2b0 net/socket.c:1468 [] sock_create net/socket.c:1519 [inline] [] __sys_socket+0x6f/0x140 net/socket.c:1561 [] __do_sys_socket net/socket.c:1570 [inline] [] __se_sys_socket net/socket.c:1568 [inline] [] __x64_sys_socket+0x1a/0x20 net/socket.c:1568 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 [] entry_SYSCALL_64_after_hwframe+0x44/0xae <...> Use mod_delayed_work() instead: if @connect_work is already scheduled, reschedule it, and undo sock_hold() to keep the reference count balanced. Reported-and-tested-by: syzbot+b03f55bf128f9a38f064@syzkaller.appspotmail.com Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Co-developed-by: Stefano Garzarella Signed-off-by: Stefano Garzarella Reviewed-by: Stefano Garzarella Signed-off-by: Peilin Ye Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/vmw_vsock/af_vsock.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1205,7 +1205,14 @@ static int vsock_stream_connect(struct s * timeout fires. */ sock_hold(sk); - schedule_delayed_work(&vsk->connect_work, timeout); + + /* If the timeout function is already scheduled, + * reschedule it, then ungrab the socket refcount to + * keep it balanced. + */ + if (mod_delayed_work(system_wq, &vsk->connect_work, + timeout)) + sock_put(sk); /* Skip ahead to preserve error code set above. */ goto out_wait;