From: Wilson Kok Date: Fri, 5 Jun 2015 07:52:57 +0000 (-0700) Subject: bridge: use _bh spinlock variant for br_fdb_update to avoid lockup X-Git-Tag: v3.4.109~18 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0b6afbdd165890743b64c57c07cbc4e6e3174b35;p=thirdparty%2Fkernel%2Fstable.git bridge: use _bh spinlock variant for br_fdb_update to avoid lockup 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 --- diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c index 5ba0c844d508c..b5597bb37e7a2 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); } }