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Chuck Lever
81246a6530
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: 3b3009ea8a ("net/handshake: Create a NETLINK service for handling handshake requests")
Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>