Commit 9fba1eb3 authored Sep 16, 2025 by Eric Dumazet Committed by Paolo Abeni Sep 18, 2025

ipv6: np->rxpmtu race annotation



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 <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250916160951.541279-4-edumazet@google.com


Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

parent 5489f333

net/ipv6/raw.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

net/ipv6/udp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -479,7 +479,7 @@ 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: