Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754097AbbFYKNl (ORCPT ); Thu, 25 Jun 2015 06:13:41 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:39792 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753208AbbFYKDb (ORCPT ); Thu, 25 Jun 2015 06:03:31 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Nikolay Aleksandrov , "David S. Miller" , Luis Henriques Subject: [PATCH 3.16.y-ckt 42/71] bridge: disable softirqs around br_fdb_update to avoid lockup Date: Thu, 25 Jun 2015 11:02:21 +0100 Message-Id: <1435226570-3669-43-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1435226570-3669-1-git-send-email-luis.henriques@canonical.com> References: <1435226570-3669-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2244 Lines: 52 3.16.7-ckt14 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Nikolay Aleksandrov 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 Signed-off-by: Luis Henriques --- 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 b524c36c1273..a10c1f87becc 100644 --- a/net/bridge/br_fdb.c +++ b/net/bridge/br_fdb.c @@ -777,9 +777,11 @@ static int __br_fdb_add(struct ndmsg *ndm, struct net_bridge_port *p, int err = 0; if (ndm->ndm_flags & NTF_USE) { + local_bh_disable(); rcu_read_lock(); br_fdb_update(p->br, p, addr, vid, true); rcu_read_unlock(); + local_bh_enable(); } else { spin_lock_bh(&p->br->hash_lock); err = fdb_add_entry(p, addr, ndm->ndm_state, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/