From: Daniel Borkmann daniel@iogearbox.net

commit 626dfed5fa3bfb41e0dffd796032b555b69f9cde upstream.

When using a BPF program on kernel_connect(), the call can return -EPERM. This causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing the kernel to potentially freeze up.

Neil suggested:

This will propagate -EPERM up into other layers which might not be ready to handle it. It might be safer to map EPERM to an error we would be more likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.

ECONNREFUSED as error seems reasonable. For programs setting a different error can be out of reach (see handling in 4fbac77d2d09) in particular on kernels which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err instead of allow boolean"), thus given that it is better to simply remap for consistent behavior. UDP does handle EPERM in xs_udp_send_request().

Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect") Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind") Co-developed-by: Lex Siegel usiegl00@gmail.com Signed-off-by: Lex Siegel usiegl00@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Cc: Neil Brown neilb@suse.de Cc: Trond Myklebust trondmy@kernel.org Cc: Anna Schumaker anna@kernel.org Link: https://github.com/cilium/cilium/issues/33395 Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.nei... Link: https://patch.msgid.link/9069ec1d59e4b2129fc23433349fd5580ad43921.1720075070... Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Hugo SIMELIERE hsimeliere.opensource@witekio.com --- net/sunrpc/xprtsock.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 938c649c5c9f..625b5f69d3ca 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2466,6 +2466,13 @@ static void xs_tcp_setup_socket(struct work_struct *work) case -EALREADY: xprt_unlock_connect(xprt, transport); return; + case -EPERM: + /* Happens, for instance, if a BPF program is preventing + * the connect. Remap the error so upper layers can better + * deal with it. + */ + status = -ECONNREFUSED; + /* fall through */ case -EINVAL: /* Happens, for instance, if the user specified a link * local IPv6 address without a scope-id.