bpf: sockhash, disallow bpf_tcp_close and update in parallel

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+b680e42077a0d7c9a0c4@syzkaller.appspotmail.com
Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 00fb2e328d1b..9c67e96fe336 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;
 }