soreuseport: fix initialization race
[ Upstream commit 1b5f962e71bfad6284574655c406597535c3ea7a ]
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 <kraig@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 4363b1e..bef4a94 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -222,10 +222,7 @@
}
}
- /* 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);
}
/**