From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754991AbbIOJMj (ORCPT ); Tue, 15 Sep 2015 05:12:39 -0400 Received: from mail.kernel.org ([198.145.29.136]:53656 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754983AbbIOJMf (ORCPT ); Tue, 15 Sep 2015 05:12:35 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nikolay Aleksandrov , "David S. Miller" , Zefan Li Subject: [PATCH 3.4 129/146] bridge: disable softirqs around br_fdb_update to avoid lockup Date: Tue, 15 Sep 2015 17:04:04 +0800 Message-Id: <1442307861-32031-129-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442307787-31952-1-git-send-email-lizf@kernel.org> References: <1442307787-31952-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nikolay Aleksandrov 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit c4c832f89dc468cf11dc0dd17206bace44526651 upstream. br_fdb_update() can be called in process context in the following way: br_fdb_add() -> __br_fdb_add() -> br_fdb_update() (if NTF_USE flag is set) so we need to disable softirqs because there are softirq users of the hash_lock. One easy way to reproduce this is to modify the bridge utility to set NTF_USE, enable stp and then set maxageing to a low value so br_fdb_cleanup() is called frequently and then just add new entries in a loop. This happens because br_fdb_cleanup() is called from timer/softirq context. The spin locks in br_fdb_update were _bh before commit f8ae737deea1 ("[BRIDGE]: forwarding remove unneeded preempt and bh diasables") and at the time that commit was correct because br_fdb_update() couldn't be called from process context, but that changed after commit: 292d1398983f ("bridge: add NTF_USE support") Using local_bh_disable/enable around br_fdb_update() allows us to keep using the spin_lock/unlock in br_fdb_update for the fast-path. Signed-off-by: Nikolay Aleksandrov Fixes: 292d1398983f ("bridge: add NTF_USE support") Signed-off-by: David S. Miller [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- net/bridge/br_fdb.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c index b5597bb..3cb93e8 100644 --- a/net/bridge/br_fdb.c +++ b/net/bridge/br_fdb.c @@ -665,9 +665,11 @@ int br_fdb_add(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg) } if (ndm->ndm_flags & NTF_USE) { + local_bh_disable(); rcu_read_lock(); br_fdb_update(p->br, p, addr); rcu_read_unlock(); + local_bh_enable(); } else { spin_lock_bh(&p->br->hash_lock); err = fdb_add_entry(p, addr, ndm->ndm_state, nlh->nlmsg_flags); -- 1.9.1