bpf: tcp: Stop bpf_setsockopt(TCP_CONGESTION) in init ops to recur itself

[platform/kernel/linux-starfive.git] / net / core / filter.c

diff --git a/net/core/filter.c b/net/core/filter.c
index 96f2f7a..ac4c45c 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5105,6 +5105,9 @@ static int bpf_sol_tcp_setsockopt(struct sock *sk, int optname,
 static int sol_tcp_sockopt_congestion(struct sock *sk, char *optval,
                                      int *optlen, bool getopt)
 {
+       struct tcp_sock *tp;
+       int ret;
+
        if (*optlen < 2)
                return -EINVAL;
 
@@ -5125,8 +5128,31 @@ static int sol_tcp_sockopt_congestion(struct sock *sk, char *optval,
        if (*optlen >= sizeof("cdg") - 1 && !strncmp("cdg", optval, *optlen))
                return -ENOTSUPP;
 
-       return do_tcp_setsockopt(sk, SOL_TCP, TCP_CONGESTION,
+       /* It stops this looping
+        *
+        * .init => bpf_setsockopt(tcp_cc) => .init =>
+        * bpf_setsockopt(tcp_cc)" => .init => ....
+        *
+        * The second bpf_setsockopt(tcp_cc) is not allowed
+        * in order to break the loop when both .init
+        * are the same bpf prog.
+        *
+        * This applies even the second bpf_setsockopt(tcp_cc)
+        * does not cause a loop.  This limits only the first
+        * '.init' can call bpf_setsockopt(TCP_CONGESTION) to
+        * pick a fallback cc (eg. peer does not support ECN)
+        * and the second '.init' cannot fallback to
+        * another.
+        */
+       tp = tcp_sk(sk);
+       if (tp->bpf_chg_cc_inprogress)
+               return -EBUSY;
+
+       tp->bpf_chg_cc_inprogress = 1;
+       ret = do_tcp_setsockopt(sk, SOL_TCP, TCP_CONGESTION,
                                KERNEL_SOCKPTR(optval), *optlen);
+       tp->bpf_chg_cc_inprogress = 0;
+       return ret;
 }
 
 static int sol_tcp_sockopt(struct sock *sk, int optname,