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/core/sock_reuseport.c b/net/core/sock_reuseport.c
index 9a1a352..77f396b 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -36,9 +36,14 @@
* soft irq of receive path or setsockopt from process context
*/
spin_lock_bh(&reuseport_lock);
- WARN_ONCE(rcu_dereference_protected(sk->sk_reuseport_cb,
- lockdep_is_held(&reuseport_lock)),
- "multiple allocations for the same socket");
+
+ /* Allocation attempts can occur concurrently via the setsockopt path
+ * and the bind/hash path. Nothing to do when we lose the race.
+ */
+ if (rcu_dereference_protected(sk->sk_reuseport_cb,
+ lockdep_is_held(&reuseport_lock)))
+ goto out;
+
reuse = __reuseport_alloc(INIT_SOCKS);
if (!reuse) {
spin_unlock_bh(&reuseport_lock);
@@ -49,6 +54,7 @@
reuse->num_socks = 1;
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+out:
spin_unlock_bh(&reuseport_lock);
return 0;