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bridge: use _bh spinlock variant for br_fdb_update to avoid lockup

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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 f8ae737dee
("[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:
292d139898 ("bridge: add NTF_USE support")

Signed-off-by: Wilson Kok <wkok@cumulusnetworks.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Fixes: 292d139898 ("bridge: add NTF_USE support")
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wilson Kok 2015-06-05 00:52:57 -07:00 committed by David S. Miller
parent 078b29d7e9
commit 1d7c49037b
1 changed files with 2 additions and 2 deletions
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4
net/bridge/br_fdb.c
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@ -569,7 +569,7 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
fdb_notify(br, fdb, RTM_NEWNEIGH);
}
} else {
spin_lock(&br->hash_lock);
spin_lock_bh(&br->hash_lock);
if (likely(!fdb_find(head, addr, vid))) {
fdb = fdb_create(head, source, addr, vid);
if (fdb) {
@ -581,7 +581,7 @@ 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);
}
}