From c9a368f1c0fbe2e3a21ebf231caeae58b18b2681 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 8 Jul 2020 23:11:10 -0700 Subject: bpf: net: Avoid incorrect bpf_sk_reuseport_detach call bpf_sk_reuseport_detach is currently called when sk->sk_user_data is not NULL. It is incorrect because sk->sk_user_data may not be managed by the bpf's reuseport_array. It has been reported in [1] that, the bpf_sk_reuseport_detach() which is called from udp_lib_unhash() has corrupted the sk_user_data managed by l2tp. This patch solves it by using another bit (defined as SK_USER_DATA_BPF) of the sk_user_data pointer value. It marks that a sk_user_data is managed/owned by BPF. The patch depends on a PTRMASK introduced in commit f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if tagged"). [ Note: sk->sk_user_data is used by bpf's reuseport_array only when a sk is added to the bpf's reuseport_array. i.e. doing setsockopt(SO_REUSEPORT) and having "sk->sk_reuseport == 1" alone will not stop sk->sk_user_data being used by other means. ] [1]: https://lore.kernel.org/netdev/20200706121259.GA20199@katalix.com/ Fixes: 5dc4c4b7d4e8 ("bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY") Reported-by: James Chapman Reported-by: syzbot+9f092552ba9a5efca5df@syzkaller.appspotmail.com Signed-off-by: Martin KaFai Lau Signed-off-by: Daniel Borkmann Tested-by: James Chapman Acked-by: James Chapman Link: https://lore.kernel.org/bpf/20200709061110.4019316-1-kafai@fb.com --- include/net/sock.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/net') diff --git a/include/net/sock.h b/include/net/sock.h index 3428619faae4..1183507df95b 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -533,7 +533,8 @@ enum sk_pacing { * be copied. */ #define SK_USER_DATA_NOCOPY 1UL -#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY) +#define SK_USER_DATA_BPF 2UL /* Managed by BPF */ +#define SK_USER_DATA_PTRMASK ~(SK_USER_DATA_NOCOPY | SK_USER_DATA_BPF) /** * sk_user_data_is_nocopy - Test if sk_user_data pointer must not be copied -- cgit v1.2.3