From 81246a65303d9635266b1334490142caaf86a11f Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Tue, 9 Jun 2026 10:18:31 -0400 Subject: [PATCH] handshake: Require admin permission for DONE command ACCEPT and DONE are the two downcalls of the handshake genl family, both intended for use by the trusted handshake agent (tlshd). ACCEPT already requires GENL_ADMIN_PERM; DONE has no privilege check at all. The fd-lookup in handshake_nl_done_doit() only confirms that some pending handshake request exists for the supplied sockfd; it does not authenticate the sender. An unprivileged process that guesses or observes a valid sockfd can therefore submit a DONE with HANDSHAKE_A_DONE_STATUS == 0, leaving the kernel consumer to proceed as if the handshake succeeded. A non-zero status on a forged DONE tears down a legitimate in-flight handshake before tlshd can report its real result. Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests") Reviewed-by: Jeff Layton Reviewed-by: Hannes Reinecke Signed-off-by: Chuck Lever Link: https://patch.msgid.link/20260609141831.90694-1-cel@kernel.org Signed-off-by: Jakub Kicinski --- Documentation/netlink/specs/handshake.yaml | 1 + net/handshake/genl.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/Documentation/netlink/specs/handshake.yaml b/Documentation/netlink/specs/handshake.yaml index 1024297b3851..ffec12b46759 100644 --- a/Documentation/netlink/specs/handshake.yaml +++ b/Documentation/netlink/specs/handshake.yaml @@ -125,6 +125,7 @@ operations: name: done doc: Handler reports handshake completion attribute-set: done + flags: [admin-perm] do: request: attributes: diff --git a/net/handshake/genl.c b/net/handshake/genl.c index 4b20cd9cdd0e..feac1ad063ee 100644 --- a/net/handshake/genl.c +++ b/net/handshake/genl.c @@ -38,7 +38,7 @@ static const struct genl_split_ops handshake_nl_ops[] = { .doit = handshake_nl_done_doit, .policy = handshake_done_nl_policy, .maxattr = HANDSHAKE_A_DONE_REMOTE_AUTH, - .flags = GENL_CMD_CAP_DO, + .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO, }, };