[PATCH AUTOSEL 4.20 095/105] bpf: bpf_setsockopt: reset sock dst on SO_MARK changes

[Sasha Levin]

From: Peter Oskolkov <posk@xxxxxxxxxx>

[ Upstream commit f4924f24da8c7ef64195096817f3cde324091d97 ]

In sock_setsockopt() (net/core/sock.h), when SO_MARK option is used
to change sk_mark, sk_dst_reset(sk) is called. The same should be
done in bpf_setsockopt().

Fixes: 8c4b4c7e9ff0 ("bpf: Add setsockopt helper function to bpf")
Reported-by: Maciej Åenczykowski <maze@xxxxxxxxxx>
Signed-off-by: Peter Oskolkov <posk@xxxxxxxxxx>
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
Reviewed-by: Maciej Åenczykowski <maze@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/core/filter.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index fa9452406f21..e176b335ddc0 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3948,7 +3948,10 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 			sk->sk_rcvlowat = val ? : 1;
 			break;
 		case SO_MARK:
-			sk->sk_mark = val;
+			if (sk->sk_mark != val) {
+				sk->sk_mark = val;
+				sk_dst_reset(sk);
+			}
 			break;
 		default:
 			ret = -EINVAL;
-- 
2.19.1