[PATCH bpf-next 1/2] bpf: net: Avoid loading module when calling bpf_setsockopt(TCP_CONGESTION)

Martin KaFai Lau
2022-08-30T23:37:38Z

When bpf prog changes tcp-cc by calling bpf_setsockopt(TCP_CONGESTION),
it should not try to load module which may be a blocking
operation. This details was correct in the v1 [0] but missed by
mistake in the later revision in
commit cb388e7ee3a8 ("bpf: net: Change do_tcp_setsockopt() to use the sockopt's lock_sock() and capable()")

This patch fixes it by checking the has_current_bpf_ctx().

[0]: https://lore.kernel.org/bpf/20220727060921.2373314-1-kafai@fb.com/

Fixes: cb388e7ee3a8 ("bpf: net: Change do_tcp_setsockopt() to use the sockopt's lock_sock() and capable()")
Signed-off-by: Martin KaFai Lau <martin.lau@linux.dev>
---
net/ipv4/tcp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a6986f201f92..f0d79ea45ac8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3503,7 +3503,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
name[val] = 0;

sockopt_lock_sock(sk);
- err = tcp_set_congestion_control(sk, name, true,
+ err = tcp_set_congestion_control(sk, name, !has_current_bpf_ctx(),
sockopt_ns_capable(sock_net(sk)->user_ns,
CAP_NET_ADMIN));
sockopt_release_sock(sk);
--
2.30.2