diff options
| author | Eric Dumazet <edumazet@google.com> | 2019-07-18 19:28:14 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-07-18 20:33:48 -0700 |
| commit | 8d650cdedaabb33e85e9b7c517c0c71fcecc1de9 (patch) | |
| tree | ab0428e5e973eb2b4e8b1f4859a508e2c0d07859 /net | |
| parent | 269b7c5ff78264e3728b95828d219e0e0eeaec94 (diff) | |
| download | lwn-8d650cdedaabb33e85e9b7c517c0c71fcecc1de9.tar.gz lwn-8d650cdedaabb33e85e9b7c517c0c71fcecc1de9.zip | |
tcp: fix tcp_set_congestion_control() use from bpf hook
Neal reported incorrect use of ns_capable() from bpf hook.
bpf_setsockopt(...TCP_CONGESTION...)
-> tcp_set_congestion_control()
-> ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)
-> ns_capable_common()
-> current_cred()
-> rcu_dereference_protected(current->cred, 1)
Accessing 'current' in bpf context makes no sense, since packets
are processed from softirq context.
As Neal stated : The capability check in tcp_set_congestion_control()
was written assuming a system call context, and then was reused from
a BPF call site.
The fix is to add a new parameter to tcp_set_congestion_control(),
so that the ns_capable() call is only performed under the right
context.
Fixes: 91b5b21c7c16 ("bpf: Add support for changing congestion control")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Lawrence Brakmo <brakmo@fb.com>
Reported-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/filter.c | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp.c | 4 | ||||
| -rw-r--r-- | net/ipv4/tcp_cong.c | 6 |
3 files changed, 7 insertions, 5 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 0f6854ccf894..4e2a79b2fd77 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4335,7 +4335,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, TCP_CA_NAME_MAX-1)); name[TCP_CA_NAME_MAX-1] = 0; ret = tcp_set_congestion_control(sk, name, false, - reinit); + reinit, true); } else { struct tcp_sock *tp = tcp_sk(sk); diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 7846afacdf0b..776905899ac0 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2785,7 +2785,9 @@ static int do_tcp_setsockopt(struct sock *sk, int level, name[val] = 0; lock_sock(sk); - err = tcp_set_congestion_control(sk, name, true, true); + err = tcp_set_congestion_control(sk, name, true, true, + ns_capable(sock_net(sk)->user_ns, + CAP_NET_ADMIN)); release_sock(sk); return err; } diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index e1862b64a90f..c445a81d144e 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -333,7 +333,8 @@ out: * tcp_reinit_congestion_control (if the current congestion control was * already initialized. */ -int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, bool reinit) +int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, + bool reinit, bool cap_net_admin) { struct inet_connection_sock *icsk = inet_csk(sk); const struct tcp_congestion_ops *ca; @@ -369,8 +370,7 @@ int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, boo } else { err = -EBUSY; } - } else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || - ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) { + } else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin)) { err = -EPERM; } else if (!try_module_get(ca->owner)) { err = -EBUSY; |