[PATCH net 1/1] tcp: check skb is non-NULL in tcp_rto_delta_us()
From: Josh Hunt
Date: Thu Aug 22 2024 - 23:35:11 EST
There have been multiple occassions where we have crashed in this path
because packets_out suggested there were packets on the write or retransmit
queues, but in fact there weren't leading to a NULL skb being dereferenced.
While we should fix that root cause we should also just make sure the skb
is not NULL before dereferencing it. Also add a warn once here to capture
some information if/when the problem case is hit again.
Signed-off-by: Josh Hunt <johunt@xxxxxxxxxx>
---
include/net/tcp.h | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 2aac11e7e1cc..19ea6ed87880 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2433,10 +2433,19 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
static inline s64 tcp_rto_delta_us(const struct sock *sk)
{
const struct sk_buff *skb = tcp_rtx_queue_head(sk);
- u32 rto = inet_csk(sk)->icsk_rto;
- u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto);
+ u32 rto = jiffies_to_usecs(inet_csk(sk)->icsk_rto);
+
+ if (likely(skb)) {
+ u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + rto;
+
+ return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
+ } else {
+ WARN_ONCE(1,
+ "rtx queue emtpy: inflight %u tlp_high_seq %u state %u\n",
+ tcp_sk(sk)->packets_out, tcp_sk(sk)->tlp_high_seq, sk->sk_state);
+ return rto;
+ }
- return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
}
/*
--
2.34.1