linux-kernel - [PATCH 4.4 048/159] llc: avoid blocking in llc_sap

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Message-Id: <20191122100740.546114454@linuxfoundation.org>
Date:   Fri, 22 Nov 2019 11:27:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 048/159] llc: avoid blocking in llc_sap_close()

From: Cong Wang <xiyou.wangcong@...il.com>

[ 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 <xiyou.wangcong@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 82d989995d18a..95e5ced4c1339 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 e896a2c53b120..f1e442a39db8d 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