[PATCH AUTOSEL 4.14 086/103] llc: avoid blocking in llc_sap_close()

Sasha Levin
2019-11-08T11:56:59Z

From: Cong Wang <xiyou.wangcong@gmail.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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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 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