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llc: set SOCK_RCU_FREE in llc_sap_add_socket()

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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>
This commit is contained in:
Cong Wang 2018-10-11 11:15:13 -07:00 committed by David S. Miller
parent d0f068e572
commit 5a8e7aea95
1 changed files with 1 additions and 0 deletions
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1
net/llc/llc_conn.c
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@ -734,6 +734,7 @@ void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
llc_sk(sk)->sap = sap; llc_sk(sk)->sap = sap;
spin_lock_bh(&sap->sk_lock); spin_lock_bh(&sap->sk_lock);
sock_set_flag(sk, SOCK_RCU_FREE);
sap->sk_count++; sap->sk_count++;
sk_nulls_add_node_rcu(sk, laddr_hb); sk_nulls_add_node_rcu(sk, laddr_hb);
hlist_add_head(&llc->dev_hash_node, dev_hb); hlist_add_head(&llc->dev_hash_node, dev_hb);