path: root/net/dccp/ipv4.c
diff options
authorEric Dumazet <edumazet@google.com>2015-10-22 08:20:46 -0700
committerDavid S. Miller <davem@davemloft.net>2015-10-23 05:42:21 -0700
commit5e0724d027f0548511a2165a209572d48fe7a4c8 (patch)
tree709301be9b56652004047b89f4467b3c917814cd /net/dccp/ipv4.c
parentipv4: implement support for NOPREFIXROUTE ifa flag for ipv4 address (diff)
tcp/dccp: fix hashdance race for passive sessions
Multiple cpus can process duplicates of incoming ACK messages matching a SYN_RECV request socket. This is a rare event under normal operations, but definitely can happen. Only one must win the race, otherwise corruption would occur. To fix this without adding new atomic ops, we use logic in inet_ehash_nolisten() to detect the request was present in the same ehash bucket where we try to insert the new child. If request socket was not found, we have to undo the child creation. This actually removes a spin_lock()/spin_unlock() pair in reqsk_queue_unlink() for the fast path. Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets") Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp/ipv4.c')
1 files changed, 4 insertions, 2 deletions
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 59bc180b02d8..5684e14932bd 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -393,7 +393,9 @@ static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
struct sk_buff *skb,
struct request_sock *req,
- struct dst_entry *dst)
+ struct dst_entry *dst,
+ struct request_sock *req_unhash,
+ bool *own_req)
struct inet_request_sock *ireq;
struct inet_sock *newinet;
@@ -426,7 +428,7 @@ struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
if (__inet_inherit_port(sk, newsk) < 0)
goto put_and_exit;
- __inet_hash_nolisten(newsk, NULL);
+ *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
return newsk;