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Date:   Sat, 23 Feb 2019 11:07:09 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexei Starovoitov <ast@...nel.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        bpf <bpf@...r.kernel.org>, Lawrence Brakmo <brakmo@...com>
Subject: [PATCH bpf] bpf: properly check TCP_CONGESTION optlen

If caller of bpf_setsockopt() is silly passing a negative optlen
bad things happen.

Fixes: 91b5b21c7c16 ("bpf: Add support for changing congestion control")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Lawrence Brakmo <brakmo@...com>
---
 net/core/filter.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index f7d0004fc16096eb42ece3a6acf645540ee2326b..6a5d89464168f2f35f43986c1dbc0446c9390a3c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4194,8 +4194,9 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 			char name[TCP_CA_NAME_MAX];
 			bool reinit = bpf_sock->op > BPF_SOCK_OPS_NEEDS_ECN;
 
-			strncpy(name, optval, min_t(long, optlen,
-						    TCP_CA_NAME_MAX-1));
+			if (optlen < 0)
+				return -EINVAL;
+			strncpy(name, optval, min(optlen, TCP_CA_NAME_MAX - 1));
 			name[TCP_CA_NAME_MAX-1] = 0;
 			ret = tcp_set_congestion_control(sk, name, false,
 							 reinit);
-- 
2.21.0.rc0.258.g878e2cd30e-goog

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