From 8bb73ab12d939be2a03d94271b575bcfeac33e23 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 16 Sep 2025 16:09:44 +0000 Subject: [PATCH] ipv6: np->rxpmtu race annotation [ Upstream commit 9fba1eb39e2f74d2002c5cbcf1d4435d37a4f752 ] Add READ_ONCE() annotations because np->rxpmtu can be changed while udpv6_recvmsg() and rawv6_recvmsg() read it. Since this is a very rarely used feature, and that udpv6_recvmsg() and rawv6_recvmsg() read np->rxopt anyway, change the test order so that np->rxpmtu does not need to be in a hot cache line. Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250916160951.541279-4-edumazet@google.com Reviewed-by: Jakub Kicinski Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/ipv6/raw.c | 2 +- net/ipv6/udp.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c index 328419e05c815..d148f1b03c5d0 100644 --- a/net/ipv6/raw.c +++ b/net/ipv6/raw.c @@ -445,7 +445,7 @@ static int rawv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, if (flags & MSG_ERRQUEUE) return ipv6_recv_error(sk, msg, len, addr_len); - if (np->rxpmtu && np->rxopt.bits.rxpmtu) + if (np->rxopt.bits.rxpmtu && READ_ONCE(np->rxpmtu)) return ipv6_recv_rxpmtu(sk, msg, len, addr_len); skb = skb_recv_datagram(sk, flags, &err); diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 57e38e5e4be92..9b93df668025d 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -394,7 +394,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, if (flags & MSG_ERRQUEUE) return ipv6_recv_error(sk, msg, len, addr_len); - if (np->rxpmtu && np->rxopt.bits.rxpmtu) + if (np->rxopt.bits.rxpmtu && READ_ONCE(np->rxpmtu)) return ipv6_recv_rxpmtu(sk, msg, len, addr_len); try_again: -- 2.47.3