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authorLorenz Bauer <lmb@cloudflare.com>2020-02-07 10:37:12 +0000
committerDaniel Borkmann <daniel@iogearbox.net>2020-02-07 22:28:04 +0100
commit85b8ac01a421791d66c3a458a7f83cfd173fe3fa (patch)
treeb50e4a5dd262197e651fefbab87fa13317a4e4d1 /net/core
parentb9e42724888527352604260abc6717cba21421de (diff)
downloadlinux-85b8ac01a421791d66c3a458a7f83cfd173fe3fa.tar.bz2
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/core')
-rw-r--r--net/core/sock_map.c16
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);