[bpf PATCH v2 1/3] bpf: sockmap only allow ESTABLISHED sock state

[John Fastabend]

After this patch we only allow socks that are in ESTABLISHED state or
are being added via a sock_ops event that is transitioning into an
ESTABLISHED state. By allowing sock_ops events we allow users to
manage sockmaps directly from sock ops programs. The two supported
sock_ops ops are BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB and
BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB.

Similar to TLS ULP this ensures sk_user_data is correct.

Reported-by: Eric Dumazet <eduma...@google.com>
Fixes: 1aa12bdf1bfb ("bpf: sockmap, add sock close() hook to remove socks")
Signed-off-by: John Fastabend <john.fastab...@gmail.com>
---
 kernel/bpf/sockmap.c |   31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 488ef96..1f97b55 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2097,8 +2097,12 @@ static int sock_map_update_elem(struct bpf_map *map,
                return -EINVAL;
        }
 
+       /* ULPs are currently supported only for TCP sockets in ESTABLISHED
+        * state.
+        */
        if (skops.sk->sk_type != SOCK_STREAM ||
-           skops.sk->sk_protocol != IPPROTO_TCP) {
+           skops.sk->sk_protocol != IPPROTO_TCP ||
+           skops.sk->sk_state != TCP_ESTABLISHED) {
                fput(socket->file);
                return -EOPNOTSUPP;
        }
@@ -2453,6 +2457,16 @@ static int sock_hash_update_elem(struct bpf_map *map,
                return -EINVAL;
        }
 
+       /* ULPs are currently supported only for TCP sockets in ESTABLISHED
+        * state.
+        */
+       if (skops.sk->sk_type != SOCK_STREAM ||
+           skops.sk->sk_protocol != IPPROTO_TCP ||
+           skops.sk->sk_state != TCP_ESTABLISHED) {
+               fput(socket->file);
+               return -EOPNOTSUPP;
+       }
+
        lock_sock(skops.sk);
        preempt_disable();
        rcu_read_lock();
@@ -2543,10 +2557,22 @@ struct sock  *__sock_hash_lookup_elem(struct bpf_map 
*map, void *key)
        .map_check_btf = map_check_no_btf,
 };
 
+static bool bpf_is_valid_sock_op(struct bpf_sock_ops_kern *ops)
+{
+       return ops->op == BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB ||
+              ops->op == BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB;
+}
 BPF_CALL_4(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock,
           struct bpf_map *, map, void *, key, u64, flags)
 {
        WARN_ON_ONCE(!rcu_read_lock_held());
+
+       /* ULPs are currently supported only for TCP sockets in ESTABLISHED
+        * state. This checks that the sock ops triggering the update is
+        * one indicating we are (or will be soon) in an ESTABLISHED state.
+        */
+       if (!bpf_is_valid_sock_op(bpf_sock))
+               return -EOPNOTSUPP;
        return sock_map_ctx_update_elem(bpf_sock, map, key, flags);
 }
 
@@ -2565,6 +2591,9 @@ struct sock  *__sock_hash_lookup_elem(struct bpf_map 
*map, void *key)
           struct bpf_map *, map, void *, key, u64, flags)
 {
        WARN_ON_ONCE(!rcu_read_lock_held());
+
+       if (!bpf_is_valid_sock_op(bpf_sock))
+               return -EOPNOTSUPP;
        return sock_hash_ctx_update_elem(bpf_sock, map, key, flags);
 }