From 1b5f962e71bfad6284574655c406597535c3ea7a Mon Sep 17 00:00:00 2001 From: Craig Gallek Date: Thu, 19 Oct 2017 15:00:29 -0400 Subject: soreuseport: fix initialization race Syzkaller stumbled upon a way to trigger WARNING: CPU: 1 PID: 13881 at net/core/sock_reuseport.c:41 reuseport_alloc+0x306/0x3b0 net/core/sock_reuseport.c:39 There are two initialization paths for the sock_reuseport structure in a socket: Through the udp/tcp bind paths of SO_REUSEPORT sockets or through SO_ATTACH_REUSEPORT_[CE]BPF before bind. The existing implementation assumedthat the socket lock protected both of these paths when it actually only protects the SO_ATTACH_REUSEPORT path. Syzkaller triggered this double allocation by running these paths concurrently. This patch moves the check for double allocation into the reuseport_alloc function which is protected by a global spin lock. Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection") Fixes: c125e80b8868 ("soreuseport: fast reuseport TCP socket selection") Signed-off-by: Craig Gallek Signed-off-by: David S. Miller --- net/ipv4/inet_hashtables.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'net/ipv4/inet_hashtables.c') diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index 597bb4cfe805..e7d15fb0d94d 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -456,10 +456,7 @@ static int inet_reuseport_add_sock(struct sock *sk, return reuseport_add_sock(sk, sk2); } - /* Initial allocation may have already happened via setsockopt */ - if (!rcu_access_pointer(sk->sk_reuseport_cb)) - return reuseport_alloc(sk); - return 0; + return reuseport_alloc(sk); } int __inet_hash(struct sock *sk, struct sock *osk) -- cgit v1.2.3-59-g8ed1b