thunderbolt: Clamp XDomain response data copy to allocation size

tb_xdp_properties_request() derives the per-packet copy length from
the response header without checking that it fits in the previously
allocated data buffer.  A malicious peer can set its length field
larger than the declared data_length, causing memcpy to write past
the kcalloc allocation.

Clamp the per-packet copy length so that the cumulative offset
never exceeds data_len.

Fixes: cdae7c07e3 ("thunderbolt: Add support for XDomain properties")
Cc: [email protected]
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <[email protected]>
Signed-off-by: Mika Westerberg <[email protected]>

drivers/thunderbolt/xdomain.c

@@ -393,6 +393,8 @@ static int tb_xdp_properties_request(struct tb_ctl *ctl, u64 route,
 			}
 		}
 
+		if (req.offset + len > data_len)
+			len = data_len - req.offset;
 		memcpy(data + req.offset, res->data, len * 4);
 		req.offset += len;
 	} while (!data_len || req.offset < data_len);