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authorLorenz Bauer <lmb@cloudflare.com>2020-01-10 16:23:36 +0300
committerAlexei Starovoitov <ast@kernel.org>2020-01-10 21:42:23 +0300
commit2e012c74823629d9db27963c79caa3f5b2010746 (patch)
treef7076cabc30ef3bea7a5ec1485c1e8449594cb2c /net
parente7a5f1f1cd0008e5ad379270a8657e121eedb669 (diff)
downloadlinux-2e012c74823629d9db27963c79caa3f5b2010746.tar.xz
net: bpf: Don't leak time wait and request sockets
It's possible to leak time wait and request sockets via the following BPF pseudo code:   sk = bpf_skc_lookup_tcp(...) if (sk) bpf_sk_release(sk) If sk->sk_state is TCP_NEW_SYN_RECV or TCP_TIME_WAIT the refcount taken by bpf_skc_lookup_tcp is not undone by bpf_sk_release. This is because sk_flags is re-used for other data in both kinds of sockets. The check !sock_flag(sk, SOCK_RCU_FREE) therefore returns a bogus result. Check that sk_flags is valid by calling sk_fullsock. Skip checking SOCK_RCU_FREE if we already know that sk is not a full socket. Fixes: edbf8c01de5a ("bpf: add skc_lookup_tcp helper") Fixes: f7355a6c0497 ("bpf: Check sk_fullsock() before returning from bpf_sk_lookup()") Signed-off-by: Lorenz Bauer <lmb@cloudflare.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200110132336.26099-1-lmb@cloudflare.com
Diffstat (limited to 'net')
-rw-r--r--net/core/filter.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index 28b3c258188c..d22d108fc6e3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5318,8 +5318,7 @@ __bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
if (sk) {
sk = sk_to_full_sk(sk);
if (!sk_fullsock(sk)) {
- if (!sock_flag(sk, SOCK_RCU_FREE))
- sock_gen_put(sk);
+ sock_gen_put(sk);
return NULL;
}
}
@@ -5356,8 +5355,7 @@ bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
if (sk) {
sk = sk_to_full_sk(sk);
if (!sk_fullsock(sk)) {
- if (!sock_flag(sk, SOCK_RCU_FREE))
- sock_gen_put(sk);
+ sock_gen_put(sk);
return NULL;
}
}
@@ -5424,7 +5422,8 @@ static const struct bpf_func_proto bpf_sk_lookup_udp_proto = {
BPF_CALL_1(bpf_sk_release, struct sock *, sk)
{
- if (!sock_flag(sk, SOCK_RCU_FREE))
+ /* Only full sockets have sk->sk_flags. */
+ if (!sk_fullsock(sk) || !sock_flag(sk, SOCK_RCU_FREE))
sock_gen_put(sk);
return 0;
}