bpf, sockmap: Do not ignore orig_len parameter

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@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Tested-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20220302161723.3910001-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 8eb671c..929a2b0 100644 (file)
--- 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);