diff options
| author | Lorenz Bauer <lmb@cloudflare.com> | 2020-02-07 10:37:12 +0000 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-02-07 22:28:04 +0100 |
| commit | 85b8ac01a421791d66c3a458a7f83cfd173fe3fa (patch) | |
| tree | b50e4a5dd262197e651fefbab87fa13317a4e4d1 /net | |
| parent | b9e42724888527352604260abc6717cba21421de (diff) | |
bpf, sockmap: Check update requirements after locking
It's currently possible to insert sockets in unexpected states into
a sockmap, due to a TOCTTOU when updating the map from a syscall.
sock_map_update_elem checks that sk->sk_state == TCP_ESTABLISHED,
locks the socket and then calls sock_map_update_common. At this
point, the socket may have transitioned into another state, and
the earlier assumptions don't hold anymore. Crucially, it's
conceivable (though very unlikely) that a socket has become unhashed.
This breaks the sockmap's assumption that it will get a callback
via sk->sk_prot->unhash.
Fix this by checking the (fixed) sk_type and sk_protocol without the
lock, followed by a locked check of sk_state.
Unfortunately it's not possible to push the check down into
sock_(map|hash)_update_common, since BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB
run before the socket has transitioned from TCP_SYN_RECV into
TCP_ESTABLISHED.
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20200207103713.28175-1-lmb@cloudflare.com
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/sock_map.c | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/net/core/sock_map.c b/net/core/sock_map.c index 8998e356f423..36a2433e183f 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -416,14 +416,16 @@ static int sock_map_update_elem(struct bpf_map *map, void *key, ret = -EINVAL; goto out; } - if (!sock_map_sk_is_suitable(sk) || - sk->sk_state != TCP_ESTABLISHED) { + if (!sock_map_sk_is_suitable(sk)) { ret = -EOPNOTSUPP; goto out; } sock_map_sk_acquire(sk); - ret = sock_map_update_common(map, idx, sk, flags); + if (sk->sk_state != TCP_ESTABLISHED) + ret = -EOPNOTSUPP; + else + ret = sock_map_update_common(map, idx, sk, flags); sock_map_sk_release(sk); out: fput(sock->file); @@ -739,14 +741,16 @@ static int sock_hash_update_elem(struct bpf_map *map, void *key, ret = -EINVAL; goto out; } - if (!sock_map_sk_is_suitable(sk) || - sk->sk_state != TCP_ESTABLISHED) { + if (!sock_map_sk_is_suitable(sk)) { ret = -EOPNOTSUPP; goto out; } sock_map_sk_acquire(sk); - ret = sock_hash_update_common(map, key, sk, flags); + if (sk->sk_state != TCP_ESTABLISHED) + ret = -EOPNOTSUPP; + else + ret = sock_hash_update_common(map, key, sk, flags); sock_map_sk_release(sk); out: fput(sock->file); |