From f7355a6c049711ecfbeed573e43d48bee7acb83a Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Fri, 17 May 2019 14:21:17 -0700 Subject: [PATCH] bpf: Check sk_fullsock() before returning from bpf_sk_lookup() The BPF_FUNC_sk_lookup_xxx helpers return RET_PTR_TO_SOCKET_OR_NULL. Meaning a fullsock ptr and its fullsock's fields in bpf_sock can be accessed, e.g. type, protocol, mark and priority. Some new helper, like bpf_sk_storage_get(), also expects ARG_PTR_TO_SOCKET is a fullsock. bpf_sk_lookup() currently calls sk_to_full_sk() before returning. However, the ptr returned from sk_to_full_sk() is not guaranteed to be a fullsock. For example, it cannot get a fullsock if sk is in TCP_TIME_WAIT. This patch checks for sk_fullsock() before returning. If it is not a fullsock, sock_gen_put() is called if needed and then returns NULL. Fixes: 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF") Cc: Joe Stringer Signed-off-by: Martin KaFai Lau Acked-by: Joe Stringer Signed-off-by: Daniel Borkmann --- net/core/filter.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 76f1d99640e2..fdcc504d2dec 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5343,8 +5343,14 @@ __bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len, struct sock *sk = __bpf_skc_lookup(skb, tuple, len, caller_net, ifindex, proto, netns_id, flags); - if (sk) + if (sk) { sk = sk_to_full_sk(sk); + if (!sk_fullsock(sk)) { + if (!sock_flag(sk, SOCK_RCU_FREE)) + sock_gen_put(sk); + return NULL; + } + } return sk; } @@ -5375,8 +5381,14 @@ bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len, struct sock *sk = bpf_skc_lookup(skb, tuple, len, proto, netns_id, flags); - if (sk) + if (sk) { sk = sk_to_full_sk(sk); + if (!sk_fullsock(sk)) { + if (!sock_flag(sk, SOCK_RCU_FREE)) + sock_gen_put(sk); + return NULL; + } + } return sk; } -- 2.30.2