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ipv6: np->rxpmtu race annotation

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[ 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 <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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2025-09-16 16:09:44 +00:00
committed by Greg Kroah-Hartman
parent 765f8816d3
commit ec2b3f83b4
2 changed files with 2 additions and 2 deletions
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2
net/ipv6/raw.c
View File

@@ -438,7 +438,7 @@ 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);

2
net/ipv6/udp.c
View File

@@ -347,7 +347,7 @@ 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: