netdev - [PATCH net 2/4] net: proper check if we hold the socket lock during dereference

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Date:	Fri,  1 Apr 2016 01:29:40 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, sasha.levin@...cle.com,
	daniel@...earbox.net, alexei.starovoitov@...il.com,
	mkubecek@...e.cz
Subject: [PATCH net 2/4] net: proper check if we hold the socket lock during dereference

lockdep_sock_is_held makes sure that we currently own the
lock. sock_owned_by_user simply checks if a user holds the socket. This
could lead to non deterministic lock checks.

Reported-by: Sasha Levin <sasha.levin@...cle.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Michal Kubecek <mkubecek@...e.cz>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 include/net/sock.h | 5 +++++
 net/core/filter.c  | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 255d3e03727b73..30f9b5ad0a82ef 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1382,6 +1382,11 @@ static inline void unlock_sock_fast(struct sock *sk, bool slow)
 		spin_unlock_bh(&sk->sk_lock.slock);
 }
 
+static bool lockdep_sock_is_held(struct sock *sk)
+{
+	return lockdep_is_held(&sk->sk_lock) ||
+	       lockdep_is_held(&sk->sk_lock.slock);
+}
 
 struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
 		      struct proto *prot, int kern);
diff --git a/net/core/filter.c b/net/core/filter.c
index 4b81b71171b4ce..e8486ba601eae7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1166,7 +1166,7 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
 	}
 
 	old_fp = rcu_dereference_protected(sk->sk_filter,
-					   sock_owned_by_user(sk));
+					   lockdep_sock_is_held(sk));
 	rcu_assign_pointer(sk->sk_filter, fp);
 
 	if (old_fp)
@@ -2259,7 +2259,7 @@ int sk_detach_filter(struct sock *sk)
 		return -EPERM;
 
 	filter = rcu_dereference_protected(sk->sk_filter,
-					   sock_owned_by_user(sk));
+					   lockdep_sock_is_held(sk));
 	if (filter) {
 		RCU_INIT_POINTER(sk->sk_filter, NULL);
 		sk_filter_uncharge(sk, filter);
@@ -2279,7 +2279,7 @@ int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
 
 	lock_sock(sk);
 	filter = rcu_dereference_protected(sk->sk_filter,
-					   sock_owned_by_user(sk));
+					   lockdep_sock_is_held(sk));
 	if (!filter)
 		goto out;
 
-- 
2.5.5