From ed759d20249197cf87b338ff0ed328052ca3b8e7 Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Thu, 7 Feb 2013 14:21:47 +0000 Subject: oxenstored: Enforce a maximum message size of 4096 bytes The maximum size of a message is part of the protocol spec in xen/include/public/io/xs_wire.h Before this patch a client which sends an overly large message can cause a buffer read overrun. Note if a badly-behaved client sends a very large message then it will be difficult for them to make their connection work again-- they will probably need to reboot. Signed-off-by: David Scott Acked-by: Ian Campbell Committed-by: Ian Jackson --- tools/ocaml/libs/xb/partial.ml | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'tools/ocaml') diff --git a/tools/ocaml/libs/xb/partial.ml b/tools/ocaml/libs/xb/partial.ml index 3558889589..d4d1c7bdec 100644 --- a/tools/ocaml/libs/xb/partial.ml +++ b/tools/ocaml/libs/xb/partial.ml @@ -27,8 +27,15 @@ external header_size: unit -> int = "stub_header_size" external header_of_string_internal: string -> int * int * int * int = "stub_header_of_string" +let xenstore_payload_max = 4096 (* xen/include/public/io/xs_wire.h *) + let of_string s = let tid, rid, opint, dlen = header_of_string_internal s in + (* A packet which is bigger than xenstore_payload_max is illegal. + This will leave the guest connection is a bad state and will + be hard to recover from without restarting the connection + (ie rebooting the guest) *) + let dlen = min xenstore_payload_max dlen in { tid = tid; rid = rid; @@ -38,6 +45,7 @@ let of_string s = } let append pkt s sz = + if pkt.len > 4096 then failwith "Buffer.add: cannot grow buffer"; Buffer.add_string pkt.buf (String.sub s 0 sz) let to_complete pkt = -- cgit v1.2.3