All five ROSE state machines (states 1-5) handle ROSE_CLEAR_REQUEST by reading the cause and diagnostic bytes directly from skb->data[3] and skb->data[4] without verifying that the frame is long enough: rose_disconnect(sk, ..., skb->data[3], skb->data[4]); The entry-point check in rose_route_frame() only enforces ROSE_MIN_LEN (3 bytes), so a remote peer on a ROSE network can send a syntactically valid but truncated CLEAR_REQUEST (3 or 4 bytes) while a connection is open in any state. Processing such a frame causes a one- or two-byte out-of-bounds read past the skb data, leaking uninitialized heap content as the cause/diagnostic values returned to user space via getsockopt(ROSE_GETCAUSE). Add a single length check at the rose_process_rx_frame() dispatch point, before any state machine is entered, to drop frames that carry the CLEAR_REQUEST type code but are too short to contain the required cause and diagnostic fields. Cc: stable@vger.kernel.org Cc: linux-hams@vger.kernel.org Signed-off-by: Mashiro Chen --- net/rose/rose_in.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/rose/rose_in.c b/net/rose/rose_in.c index 0276b393f0e530..e2680058196273 100644 --- a/net/rose/rose_in.c +++ b/net/rose/rose_in.c @@ -271,6 +271,13 @@ int rose_process_rx_frame(struct sock *sk, struct sk_buff *skb) frametype = rose_decode(skb, &ns, &nr, &q, &d, &m); + /* + * ROSE_CLEAR_REQUEST carries cause and diagnostic in bytes 3..4. + * Reject a malformed frame that is too short to contain them. + */ + if (frametype == ROSE_CLEAR_REQUEST && skb->len < 5) + return 0; + switch (rose->state) { case ROSE_STATE_1: queued = rose_state1_machine(sk, skb, frametype); -- 2.53.0