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authorCraig Gallek <kraig@google.com>2017-10-19 22:00:29 +0300
committerDavid S. Miller <davem@davemloft.net>2017-10-22 04:03:51 +0300
commit1b5f962e71bfad6284574655c406597535c3ea7a (patch)
tree2f96c8a5f8251654c8aaf3874681cd04c02b24e8 /net/core/sock_reuseport.c
parent66c54517540cedf5a22911c6b7f5c7d8b5d1e1be (diff)
downloadlinux-1b5f962e71bfad6284574655c406597535c3ea7a.tar.xz
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 <kraig@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sock_reuseport.c')
-rw-r--r--net/core/sock_reuseport.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index eed1ebf7f29d..b1e0dbea1e8c 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -36,9 +36,14 @@ int reuseport_alloc(struct sock *sk)
* 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 @@ int reuseport_alloc(struct sock *sk)
reuse->num_socks = 1;
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+out:
spin_unlock_bh(&reuseport_lock);
return 0;