From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-516026-1519834372-2-8794873373412868708 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.249, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1519834372; b=oT5SIASUgYqbVC5HW0d246RVWJDSCUOd0B2Un/8gHnBICKX Gs2RYdz9J56sCPwRkNAHMUb9hd74Nf8aXMdJIWG0IS4IAGsfaVgZ0urdU1agdUtm to7VkX5XKrmMjU/E3kHwCa9H9Tv1kx8hBtbztURzy3SxkYEztHmg/W53GJjLp9ut /OY/CFBhZFLV9mVmmyn+fOkOSdJp3w8mfQKuClUuZleXg284X0N5iruuRbHEcktl TR7s3VPw25NJ89t6/NAw2HuBVmipZPV3ChI1hKWM64zkCOgRfIm49ZCPbW7lS0qH QWiaU17xt8zUhyQN8yv3MRwzflvQjsKfZujs//A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:content-transfer-encoding :mime-version:from:to:cc:date:message-id:subject:in-reply-to :sender:list-id; s=arctest; t=1519834372; bh=Zxo4dEvrBrRpCN0Q0DK a3KvVJCcZtlU4N//TIJhKLWs=; b=goD03qfFUYC+etNxNe80fFMhYTSCody9LD6 2rT5ioQ5FgMlxeitnY+8es2rPkUGX5pwiTbrry5Vd0IshwCJ+pKOPcO12u0N0RwJ YqTRTcJZ2d2Zk5Q0ijptoIgZSCyEhPd0ksxIGv+XSGpEPlCkeOYEiUOzRsaNf8WD Aj3CwYlb0mmVnmT+lhmSF22WyRd81zZCowb0+BIXIIAHbJqrsYoK2Hk+veHLVZJh U7uVjdweNPUrK+R6Qr4hc/Wl7TFVDBZRShiXAs39RLeDd98bWxAGqjRGEa/250Bs POvtW1QGbIKGvQINNSh60rsxR5lCCfz2jypXPSUz+esfZqT05ag== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932702AbeB1QMe (ORCPT ); Wed, 28 Feb 2018 11:12:34 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35048 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934523AbeB1QMb (ORCPT ); Wed, 28 Feb 2018 11:12:31 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Xin Long" , "Neil Horman" , "David S. Miller" Date: Wed, 28 Feb 2018 15:20:18 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 209/254] sctp: use the right sk after waking up from wait_buf sleep In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.16.55-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Xin Long commit cea0cc80a6777beb6eb643d4ad53690e1ad1d4ff upstream. Commit dfcb9f4f99f1 ("sctp: deny peeloff operation on asocs with threads sleeping on it") fixed the race between peeloff and wait sndbuf by checking waitqueue_active(&asoc->wait) in sctp_do_peeloff(). But it actually doesn't work, as even if waitqueue_active returns false the waiting sndbuf thread may still not yet hold sk lock. After asoc is peeled off, sk is not asoc->base.sk any more, then to hold the old sk lock couldn't make assoc safe to access. This patch is to fix this by changing to hold the new sk lock if sk is not asoc->base.sk, meanwhile, also set the sk in sctp_sendmsg with the new sk. With this fix, there is no more race between peeloff and waitbuf, the check 'waitqueue_active' in sctp_do_peeloff can be removed. Thanks Marcelo and Neil for making this clear. v1->v2: fix it by changing to lock the new sock instead of adding a flag in asoc. Suggested-by: Neil Horman Signed-off-by: Xin Long Acked-by: Neil Horman Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/sctp/socket.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -82,8 +82,8 @@ /* Forward declarations for internal helper functions. */ static int sctp_writeable(struct sock *sk); static void sctp_wfree(struct sk_buff *skb); -static int sctp_wait_for_sndbuf(struct sctp_association *, long *timeo_p, - size_t msg_len); +static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p, + size_t msg_len, struct sock **orig_sk); static int sctp_wait_for_packet(struct sock *sk, int *err, long *timeo_p); static int sctp_wait_for_connect(struct sctp_association *, long *timeo_p); static int sctp_wait_for_accept(struct sock *sk, long timeo); @@ -1905,7 +1905,8 @@ static int sctp_sendmsg(struct kiocb *io timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); if (!sctp_wspace(asoc)) { - err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len); + /* sk can be changed by peel off when waiting for buf. */ + err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len, &sk); if (err) goto out_free; } @@ -4335,12 +4336,6 @@ int sctp_do_peeloff(struct sock *sk, sct if (!asoc) return -EINVAL; - /* If there is a thread waiting on more sndbuf space for - * sending on this asoc, it cannot be peeled. - */ - if (waitqueue_active(&asoc->wait)) - return -EBUSY; - /* An association cannot be branched off from an already peeled-off * socket, nor is this supported for tcp style sockets. */ @@ -6737,7 +6732,7 @@ void sctp_sock_rfree(struct sk_buff *skb /* Helper function to wait for space in the sndbuf. */ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p, - size_t msg_len) + size_t msg_len, struct sock **orig_sk) { struct sock *sk = asoc->base.sk; int err = 0; @@ -6770,11 +6765,17 @@ static int sctp_wait_for_sndbuf(struct s release_sock(sk); current_timeo = schedule_timeout(current_timeo); lock_sock(sk); + if (sk != asoc->base.sk) { + release_sock(sk); + sk = asoc->base.sk; + lock_sock(sk); + } *timeo_p = current_timeo; } out: + *orig_sk = sk; finish_wait(&asoc->wait, &wait); /* Release the association's refcnt. */