From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Wilson Kok , Nikolay Aleksandrov , "David S. Miller" , Zefan Li Subject: [PATCH 3.4 128/146] bridge: use _bh spinlock variant for br_fdb_update to avoid lockup Date: Tue, 15 Sep 2015 17:04:03 +0800 Message-Id: <1442307861-32031-128-git-send-email-lizf@kernel.org> 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: From: Wilson Kok 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 1d7c49037b12016e7056b9f2c990380e2187e766 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 use spin_lock_bh 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. These locks 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") Signed-off-by: Wilson Kok 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 | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c index 5ba0c84..b5597bb 100644 --- a/net/bridge/br_fdb.c +++ b/net/bridge/br_fdb.c @@ -440,7 +440,7 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source, fdb->updated = jiffies; } } else { - spin_lock(&br->hash_lock); + spin_lock_bh(&br->hash_lock); if (likely(!fdb_find(head, addr))) { fdb = fdb_create(head, source, addr); if (fdb) @@ -449,7 +449,7 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source, /* else we lose race and someone else inserts * it first, don't bother updating */ - spin_unlock(&br->hash_lock); + spin_unlock_bh(&br->hash_lock); } } -- 1.9.1