[PATCH AUTOSEL 4.9 92/99] sock: Reset dst when changing sk_mark via setsockopt

Sasha Levin
2019-11-16T15:53:31Z

From: David Barmann <david.barmann@stackpath.com>

[ Upstream commit 50254256f382c56bde87d970f3d0d02fdb76ec70 ]

When setting the SO_MARK socket option, if the mark changes, the dst
needs to be reset so that a new route lookup is performed.

This fixes the case where an application wants to change routing by
setting a new sk_mark. If this is done after some packets have already
been sent, the dst is cached and has no effect.

Signed-off-by: David Barmann <david.barmann@stackpath.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/sock.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index d224933514074..9178c16543758 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -945,10 +945,12 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
clear_bit(SOCK_PASSSEC, &sock->flags);
break;
case SO_MARK:
- if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
+ if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
ret = -EPERM;
- else
+ } else if (val != sk->sk_mark) {
sk->sk_mark = val;
+ sk_dst_reset(sk);
+ }
break;

case SO_RXQ_OVFL:
--
2.20.1