[PATCH nf 1/2] netfilter: nf_conncount: use spin_lock_bh instead of spin_lock

[Taehee Yoo]

conn_free() holds lock with spin_lock(). and it is called by both
nf_conncount_lookup() and nf_conncount_gc_list().
nf_conncount_lookup() is bottom-half context and nf_conncount_gc_list()
is process context. so that spin_lock() is not safe.
Hence conn_free() should use spin_lock_bh() instead of spin_lock().

test commands:
   %nft add table ip filter
   %nft add chain ip filter input { type filter hook input priority 0\; }
   %nft add rule filter input meter test { ip saddr ct count over 2 } \
           counter

splat looks like:
[  461.996507] ================================
[  461.998999] WARNING: inconsistent lock state
[  461.998999] 4.19.0-rc6+ #22 Not tainted
[  461.998999] --------------------------------
[  461.998999] inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
[  461.998999] kworker/0:2/134 [HC0[0]:SC0[0]:HE1:SE1] takes:
[  461.998999] 00000000a71a559a (&(&list->list_lock)->rlock){+.?.}, at: 
conn_free+0x69/0x2b0 [nf_conncount]
[  461.998999] {IN-SOFTIRQ-W} state was registered at:
[  461.998999]   _raw_spin_lock+0x30/0x70
[  461.998999]   nf_conncount_add+0x28a/0x520 [nf_conncount]
[  461.998999]   nft_connlimit_eval+0x401/0x580 [nft_connlimit]
[  461.998999]   nft_dynset_eval+0x32b/0x590 [nf_tables]
[  461.998999]   nft_do_chain+0x497/0x1430 [nf_tables]
[  461.998999]   nft_do_chain_ipv4+0x255/0x330 [nf_tables]
[  461.998999]   nf_hook_slow+0xb1/0x160
[ ... ]
[  461.998999] other info that might help us debug this:
[  461.998999]  Possible unsafe locking scenario:
[  461.998999]
[  461.998999]        CPU0
[  461.998999]        ----
[  461.998999]   lock(&(&list->list_lock)->rlock);
[  461.998999]   <Interrupt>
[  461.998999]     lock(&(&list->list_lock)->rlock);
[  461.998999]
[  461.998999]  *** DEADLOCK ***
[  461.998999]
[ ... ]

Fixes: 5c789e131cbb ("netfilter: nf_conncount: Add list lock and gc worker, and 
RCU for init tree search")
Signed-off-by: Taehee Yoo <ap420...@gmail.com>
---
 net/netfilter/nf_conncount.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c
index 02ca7df793f5..8c6ece33b31f 100644
--- a/net/netfilter/nf_conncount.c
+++ b/net/netfilter/nf_conncount.c
@@ -132,10 +132,10 @@ static bool conn_free(struct nf_conncount_list *list,
 {
        bool free_entry = false;
 
-       spin_lock(&list->list_lock);
+       spin_lock_bh(&list->list_lock);
 
        if (list->count == 0) {
-               spin_unlock(&list->list_lock);
+               spin_unlock_bh(&list->list_lock);
                 return free_entry;
        }
 
@@ -144,7 +144,7 @@ static bool conn_free(struct nf_conncount_list *list,
        if (list->count == 0)
                free_entry = true;
 
-       spin_unlock(&list->list_lock);
+       spin_unlock_bh(&list->list_lock);
        call_rcu(&conn->rcu_head, __conn_free);
        return free_entry;
 }
-- 
2.17.1