[PATCH net-next 13/20] tcp: annotate data-races on tp->segs_in and tp->data_segs_in
From: Eric Dumazet <hidden>
Date: 2021-11-15 20:09:37
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> tcp_segs_in() can be called from BH, while socket spinlock is held but socket owned by user, eventually reading these fields from tcp_get_info() Found by code inspection, no need to backport this patch to older kernels. Signed-off-by: Eric Dumazet <edumazet@google.com> --- include/net/tcp.h | 8 ++++++-- net/ipv4/tcp.c | 6 ++++-- 2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4da22b41bde688dec4a3741f510346dae0cf32e0..05c81677aaf782f23b8c63d6ed133df802b43064 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h@@ -2172,9 +2172,13 @@ static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb) u16 segs_in; segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs); - tp->segs_in += segs_in; + + /* We update these fields while other threads might + * read them from tcp_get_info() + */ + WRITE_ONCE(tp->segs_in, tp->segs_in + segs_in); if (skb->len > tcp_hdrlen(skb)) - tp->data_segs_in += segs_in; + WRITE_ONCE(tp->data_segs_in, tp->data_segs_in + segs_in); } /*
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 24d77a32c9cbcdf0e4380ec6d9aa3e42d2cf8730..267b2b18f048c4df4cabd819433a99bf8b3f2678 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -3769,10 +3769,12 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) tcp_get_info_chrono_stats(tp, info); info->tcpi_segs_out = tp->segs_out; - info->tcpi_segs_in = tp->segs_in; + + /* segs_in and data_segs_in can be updated from tcp_segs_in() from BH */ + info->tcpi_segs_in = READ_ONCE(tp->segs_in); + info->tcpi_data_segs_in = READ_ONCE(tp->data_segs_in); info->tcpi_min_rtt = tcp_min_rtt(tp); - info->tcpi_data_segs_in = tp->data_segs_in; info->tcpi_data_segs_out = tp->data_segs_out; info->tcpi_delivery_rate_app_limited = tp->rate_app_limited ? 1 : 0;
--
2.34.0.rc1.387.gb447b232ab-goog