Subject: [PATCH AUTOSEL 4.19 172/205] llc: avoid blocking in llc_sap_close()

From: Sasha Levin <[email-masked]>
Date: Fri, 8 Nov 2019 06:37:19 -0500

From: Cong Wang <[email-masked]>

[ Upstream commit 9708d2b5b7c648e8e0a40d11e8cea12f6277f33c ]

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 <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 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 890a87318014d..df282d9b40170 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 260b3dc1b4a2a..64d4bef04e730 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 = {
-- 
2.20.1