| From foo@baz Sat Jun 13 09:48:35 PDT 2015 |
| From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> |
| Date: Sat, 6 Jun 2015 06:49:00 -0700 |
| Subject: bridge: disable softirqs around br_fdb_update to avoid lockup |
| |
| From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> |
| |
| [ Upstream commit c4c832f89dc468cf11dc0dd17206bace44526651 ] |
| |
| 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 <nikolay@cumulusnetworks.com> |
| Fixes: 292d1398983f ("bridge: add NTF_USE support") |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/bridge/br_fdb.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| --- a/net/bridge/br_fdb.c |
| +++ b/net/bridge/br_fdb.c |
| @@ -796,9 +796,11 @@ static int __br_fdb_add(struct ndmsg *nd |
| 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, |