[Patch net-next] llc: avoid blocking in llc_sap_close()

[Patch net-next] llc: avoid blocking in llc_sap_close()

[Cong Wang]

llc_sap_close() is called by llc_sap_put() which
could be called in BH context in llc_rcv(). We can't
block in BH.

There is no reason to block it here, kfree_rcu() should
be sufficient.

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 include/net/llc.h  | 1 +
 net/llc/llc_core.c | 4 +---
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/net/llc.h b/include/net/llc.h
index 890a87318014..df282d9b4017 100644
--- a/include/net/llc.h
+++ b/include/net/llc.h
@@ -66,6 +66,7 @@ struct llc_sap {
 	int sk_count;
 	struct hlist_nulls_head sk_laddr_hash[LLC_SK_LADDR_HASH_ENTRIES];
 	struct hlist_head sk_dev_hash[LLC_SK_DEV_HASH_ENTRIES];
+	struct rcu_head rcu;
 };
 
 static inline
diff --git a/net/llc/llc_core.c b/net/llc/llc_core.c
index 260b3dc1b4a2..64d4bef04e73 100644
--- a/net/llc/llc_core.c
+++ b/net/llc/llc_core.c
@@ -127,9 +127,7 @@ void llc_sap_close(struct llc_sap *sap)
 	list_del_rcu(&sap->node);
 	spin_unlock_bh(&llc_sap_list_lock);
 
-	synchronize_rcu();
-
-	kfree(sap);
+	kfree_rcu(sap, rcu);
 }
 
 static struct packet_type llc_packet_type __read_mostly = {
-- 
2.14.4

Re: [Patch net-next] llc: avoid blocking in llc_sap_close()

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue, 11 Sep 2018 11:42:06 -0700

> llc_sap_close() is called by llc_sap_put() which
> could be called in BH context in llc_rcv(). We can't
> block in BH.
> 
> There is no reason to block it here, kfree_rcu() should
> be sufficient.
> 
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied, thanks Cong.