netdev - [PATCH net 1/2] bpf, sockmap: Do not ignore orig

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Message-Id: <20220302161723.3910001-1-eric.dumazet@gmail.com>
Date:   Wed,  2 Mar 2022 08:17:22 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>
Cc:     netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net 1/2] bpf, sockmap: Do not ignore orig_len parameter

From: Eric Dumazet <edumazet@...gle.com>

Currently, sk_psock_verdict_recv() returns skb->len

This is problematic because tcp_read_sock() might have
passed orig_len < skb->len, due to the presence of TCP urgent data.

This causes an infinite loop from tcp_read_sock()

Followup patch will make tcp_read_sock() more robust vs bad actors.

Fixes: ef5659280eb1 ("bpf, sockmap: Allow skipping sk_skb parser program")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: John Fastabend <john.fastabend@...il.com>
Acked-by: Jakub Sitnicki <jakub@...udflare.com>
Tested-by: Jakub Sitnicki <jakub@...udflare.com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
 net/core/skmsg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 8eb671c827f90f1f3d2514163fc82998c9906cb6..929a2b096b04e01b85bff0a69209413abe86102d 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1153,7 +1153,7 @@ static int sk_psock_verdict_recv(read_descriptor_t *desc, struct sk_buff *skb,
 	struct sk_psock *psock;
 	struct bpf_prog *prog;
 	int ret = __SK_DROP;
-	int len = skb->len;
+	int len = orig_len;
 
 	/* clone here so sk_eat_skb() in tcp_read_sock does not drop our data */
 	skb = skb_clone(skb, GFP_ATOMIC);
-- 
2.35.1.574.g5d30c73bfb-goog