[bpf PATCH v2 2/4] bpf: sockhash, disallow bpf_tcp_close and update in parallel

[John Fastabend]

After latest lock updates there is no longer anything preventing a
close and recvmsg call running in parallel. Additionally, we can
race update with close if we close a socket and simultaneously update
if via the BPF userspace API (note the cgroup ops are already run
with sock_lock held).

To resolve this take sock_lock in close and update paths.

Reported-by: syzbot+b680e42077a0d7c9a...@syzkaller.appspotmail.com
Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close")
Signed-off-by: John Fastabend <john.fastab...@gmail.com>
---
 kernel/bpf/sockmap.c |   15 +++++++++++++++
 kernel/bpf/syscall.c |    4 +++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 00fb2e3..9c67e96 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -312,10 +312,12 @@ static void bpf_tcp_close(struct sock *sk, long timeout)
        struct smap_psock *psock;
        struct sock *osk;
 
+       lock_sock(sk);
        rcu_read_lock();
        psock = smap_psock_sk(sk);
        if (unlikely(!psock)) {
                rcu_read_unlock();
+               release_sock(sk);
                return sk->sk_prot->close(sk, timeout);
        }
 
@@ -371,6 +373,7 @@ static void bpf_tcp_close(struct sock *sk, long timeout)
                e = psock_map_pop(sk, psock);
        }
        rcu_read_unlock();
+       release_sock(sk);
        close_fun(sk, timeout);
 }
 
@@ -2069,7 +2072,13 @@ static int sock_map_update_elem(struct bpf_map *map,
                return -EOPNOTSUPP;
        }
 
+       lock_sock(skops.sk);
+       preempt_disable();
+       rcu_read_lock();
        err = sock_map_ctx_update_elem(&skops, map, key, flags);
+       rcu_read_unlock();
+       preempt_enable();
+       release_sock(skops.sk);
        fput(socket->file);
        return err;
 }
@@ -2410,7 +2419,13 @@ static int sock_hash_update_elem(struct bpf_map *map,
                return -EINVAL;
        }
 
+       lock_sock(skops.sk);
+       preempt_disable();
+       rcu_read_lock();
        err = sock_hash_ctx_update_elem(&skops, map, key, flags);
+       rcu_read_unlock();
+       preempt_enable();
+       release_sock(skops.sk);
        fput(socket->file);
        return err;
 }
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d10ecd7..a31a1ba 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -735,7 +735,9 @@ static int map_update_elem(union bpf_attr *attr)
        if (bpf_map_is_dev_bound(map)) {
                err = bpf_map_offload_update_elem(map, key, value, attr->flags);
                goto out;
-       } else if (map->map_type == BPF_MAP_TYPE_CPUMAP) {
+       } else if (map->map_type == BPF_MAP_TYPE_CPUMAP ||
+                  map->map_type == BPF_MAP_TYPE_SOCKHASH ||
+                  map->map_type == BPF_MAP_TYPE_SOCKMAP) {
                err = map->ops->map_update_elem(map, key, value, attr->flags);
                goto out;
        }