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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        =?UTF-8?q?Maciej=20=C5=BBenczykowski?= <maze@google.com>,
        Peter Oskolkov <posk@google.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.20 112/183] bpf: bpf_setsockopt: reset sock dst on SO_MARK changes
Date:   Mon, 25 Feb 2019 22:11:25 +0100
Message-Id: <20190225195113.542965529@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ 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 Żenczykowski <maze@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 fa9452406f214..e176b335ddc09 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