4.9-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 5a8e7aea953bdb6d4da13aff6f1e7f9c62023499 ]
WHen an llc sock is added into the sk_laddr_hash of an llc_sap, it is not marked with SOCK_RCU_FREE.
This causes that the sock could be freed while it is still being read by __llc_lookup_established() with RCU read lock. sock is refcounted, but with RCU read lock, nothing prevents the readers getting a zero refcnt.
Fix it by setting SOCK_RCU_FREE in llc_sap_add_socket().
Reported-by: syzbot+11e05f04c15e03be5254@syzkaller.appspotmail.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/llc/llc_conn.c | 1 + 1 file changed, 1 insertion(+)
--- a/net/llc/llc_conn.c +++ b/net/llc/llc_conn.c @@ -734,6 +734,7 @@ void llc_sap_add_socket(struct llc_sap * llc_sk(sk)->sap = sap;
spin_lock_bh(&sap->sk_lock); + sock_set_flag(sk, SOCK_RCU_FREE); sap->sk_count++; sk_nulls_add_node_rcu(sk, laddr_hb); hlist_add_head(&llc->dev_hash_node, dev_hb);