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tcp: add rcu protection around tp->fastopen_rsk

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Both tcp_v4_err() and tcp_v6_err() do the following operations
while they do not own the socket lock :

	fastopen = tp->fastopen_rsk;
 	snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;

The problem is that without appropriate barrier, the compiler
might reload tp->fastopen_rsk and trigger a NULL deref.

request sockets are protected by RCU, we can simply add
the missing annotations and barriers to solve the issue.

Fixes: 168a8f5805 ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2019-10-10 20:17:38 -07:00
committed by David S. Miller
parent 8caf8a91f3
commit d983ea6f16
11 changed files with 35 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
net/ipv4/tcp_input.c
View File

@ -2666,7 +2666,7 @@ static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
struct tcp_sock *tp = tcp_sk(sk);
bool recovered = !before(tp->snd_una, tp->high_seq);
if ((flag & FLAG_SND_UNA_ADVANCED || tp->fastopen_rsk) &&
if ((flag & FLAG_SND_UNA_ADVANCED || rcu_access_pointer(tp->fastopen_rsk)) &&
tcp_try_undo_loss(sk, false))
return;
@ -2990,7 +2990,7 @@ void tcp_rearm_rto(struct sock *sk)
/* If the retrans timer is currently being used by Fast Open
* for SYN-ACK retrans purpose, stay put.
*/
if (tp->fastopen_rsk)
if (rcu_access_pointer(tp->fastopen_rsk))
return;
if (!tp->packets_out) {
@ -6087,6 +6087,8 @@ reset_and_undo:
static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
{
struct request_sock *req;
tcp_try_undo_loss(sk, false);
/* Reset rtx states to prevent spurious retransmits_timed_out() */
@ -6096,7 +6098,9 @@ static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
* we no longer need req so release it.
*/
reqsk_fastopen_remove(sk, tcp_sk(sk)->fastopen_rsk, false);
req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
lockdep_sock_is_held(sk));
reqsk_fastopen_remove(sk, req, false);
/* Re-arm the timer because data may have been sent out.
* This is similar to the regular data transmission case
@ -6171,7 +6175,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
tcp_mstamp_refresh(tp);
tp->rx_opt.saw_tstamp = 0;
req = tp->fastopen_rsk;
req = rcu_dereference_protected(tp->fastopen_rsk,
lockdep_sock_is_held(sk));
if (req) {
bool req_stolen;