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authorEric Dumazet <edumazet@google.com>2019-07-18 19:28:14 -0700
committerDavid S. Miller <davem@davemloft.net>2019-07-18 20:33:48 -0700
commit8d650cdedaabb33e85e9b7c517c0c71fcecc1de9 (patch)
treeab0428e5e973eb2b4e8b1f4859a508e2c0d07859
parent269b7c5ff78264e3728b95828d219e0e0eeaec94 (diff)
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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>
-rw-r--r--include/net/tcp.h3
-rw-r--r--net/core/filter.c2
-rw-r--r--net/ipv4/tcp.c4
-rw-r--r--net/ipv4/tcp_cong.c6
4 files changed, 9 insertions, 6 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index cca3c59b98bf..f42d300f0cfa 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1064,7 +1064,8 @@ void tcp_get_default_congestion_control(struct net *net, char *name);
void tcp_get_available_congestion_control(char *buf, size_t len);
void tcp_get_allowed_congestion_control(char *buf, size_t len);
int tcp_set_allowed_congestion_control(char *allowed);
-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);
u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
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;