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,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 EAD2DC3A5A6 for ; Tue, 27 Aug 2019 08:02:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1E72206BA for ; Tue, 27 Aug 2019 08:02:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566892927; bh=vVk9Sb/DjoIiqL2j89SBhyyPPoSvb/UenDQ1/pyI9Y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=qy9YLu45EqrcAJTPdyV4B/871dsU4P+hnKzL36uL+KdTLC/rNe/UBpMJQTEy3L0lU lALrLSOGqQXUiPi5Mp3g6UcSQVn68D/PGrwn3qH4/I3RSVluAH3QrqQp3wxWt1aL8N RsPKExxRurGd7y8JNn6M4Vw77y4P8U06gknnjq/k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729855AbfH0ICE (ORCPT ); Tue, 27 Aug 2019 04:02:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:58294 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726071AbfH0IBr (ORCPT ); Tue, 27 Aug 2019 04:01:47 -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 09792206BF; Tue, 27 Aug 2019 08:01:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566892906; bh=vVk9Sb/DjoIiqL2j89SBhyyPPoSvb/UenDQ1/pyI9Y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YJv/8O/8jrJrb1op24iD47NoIWJ+avET5L5adKJu8gc/HUUtD6VBaHAiq7lnE6cAc 6vKqX9IIWHRnoflPan7nZxlGfePsiPD68K9HyQklbiE2/ALSiYtpAbTpUsxgV76ZyP 0JmWHuB07WzUaCTvk6KmvW9uPG1T2xqk1fnVQx/s= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+72af434e4b3417318f84@syzkaller.appspotmail.com, David Howells , Marc Dionne , Jeffrey Altman , Sasha Levin Subject: [PATCH 5.2 053/162] rxrpc: Fix potential deadlock Date: Tue, 27 Aug 2019 09:49:41 +0200 Message-Id: <20190827072740.054489358@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190827072738.093683223@linuxfoundation.org> References: <20190827072738.093683223@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit 60034d3d146b11922ab1db613bce062dddc0327a ] There is a potential deadlock in rxrpc_peer_keepalive_dispatch() whereby rxrpc_put_peer() is called with the peer_hash_lock held, but if it reduces the peer's refcount to 0, rxrpc_put_peer() calls __rxrpc_put_peer() - which the tries to take the already held lock. Fix this by providing a version of rxrpc_put_peer() that can be called in situations where the lock is already held. The bug may produce the following lockdep report: ============================================ WARNING: possible recursive locking detected 5.2.0-next-20190718 #41 Not tainted -------------------------------------------- kworker/0:3/21678 is trying to acquire lock: 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh /./include/linux/spinlock.h:343 [inline] 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: __rxrpc_put_peer /net/rxrpc/peer_object.c:415 [inline] 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: rxrpc_put_peer+0x2d3/0x6a0 /net/rxrpc/peer_object.c:435 but task is already holding lock: 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh /./include/linux/spinlock.h:343 [inline] 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:378 [inline] 00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: rxrpc_peer_keepalive_worker+0x6b3/0xd02 /net/rxrpc/peer_event.c:430 Fixes: 330bdcfadcee ("rxrpc: Fix the keepalive generator [ver #2]") Reported-by: syzbot+72af434e4b3417318f84@syzkaller.appspotmail.com Signed-off-by: David Howells Reviewed-by: Marc Dionne Reviewed-by: Jeffrey Altman Signed-off-by: Sasha Levin --- net/rxrpc/ar-internal.h | 1 + net/rxrpc/peer_event.c | 2 +- net/rxrpc/peer_object.c | 18 ++++++++++++++++++ 3 files changed, 20 insertions(+), 1 deletion(-) diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 80335b4ee4fd6..822f45386e311 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -1061,6 +1061,7 @@ void rxrpc_destroy_all_peers(struct rxrpc_net *); struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *); struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *); void rxrpc_put_peer(struct rxrpc_peer *); +void rxrpc_put_peer_locked(struct rxrpc_peer *); /* * proc.c diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c index 9f2f45c09e583..7666ec72d37e5 100644 --- a/net/rxrpc/peer_event.c +++ b/net/rxrpc/peer_event.c @@ -378,7 +378,7 @@ static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet, spin_lock_bh(&rxnet->peer_hash_lock); list_add_tail(&peer->keepalive_link, &rxnet->peer_keepalive[slot & mask]); - rxrpc_put_peer(peer); + rxrpc_put_peer_locked(peer); } spin_unlock_bh(&rxnet->peer_hash_lock); diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c index 9d3ce81cf8ae8..9c3ac96f71cbf 100644 --- a/net/rxrpc/peer_object.c +++ b/net/rxrpc/peer_object.c @@ -436,6 +436,24 @@ void rxrpc_put_peer(struct rxrpc_peer *peer) } } +/* + * Drop a ref on a peer record where the caller already holds the + * peer_hash_lock. + */ +void rxrpc_put_peer_locked(struct rxrpc_peer *peer) +{ + const void *here = __builtin_return_address(0); + int n; + + n = atomic_dec_return(&peer->usage); + trace_rxrpc_peer(peer, rxrpc_peer_put, n, here); + if (n == 0) { + hash_del_rcu(&peer->hash_link); + list_del_init(&peer->keepalive_link); + kfree_rcu(peer, rcu); + } +} + /* * Make sure all peer records have been discarded. */ -- 2.20.1