From ab21bb1971a7fa9308053b0686f43277f6e8a6c9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Edwin=20T=C3=B6r=C3=B6k?= Date: Thu, 28 Jul 2022 17:08:15 +0100 Subject: [PATCH 63/87] tools/ocaml/xenstored: Check for maxrequests before performing operations MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously we'd perform the operation, record the updated tree in the transaction record, then try to insert a watchop path and the reply packet. If we exceeded max requests we would've returned EQUOTA, but still: * have performed the operation on the transaction's tree * have recorded the watchop, making this queue effectively unbounded It is better if we check whether we'd have room to store the operation before performing the transaction, and raise EQUOTA there. Then the transaction record won't grow. This is part of XSA-326 / CVE-2022-42317. Signed-off-by: Edwin Török Acked-by: Christian Lindig (cherry picked from commit 329f4d1a6535c6c5a34025ca0d03fc5c7228fcff) --- tools/ocaml/xenstored/process.ml | 4 +++- tools/ocaml/xenstored/transaction.ml | 16 ++++++++++++---- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml index 27790d4a5c41..dd58e6979cf9 100644 --- a/tools/ocaml/xenstored/process.ml +++ b/tools/ocaml/xenstored/process.ml @@ -389,6 +389,7 @@ let input_handle_error ~cons ~doms ~fct ~con ~t ~req = let reply_error e = Packet.Error e in try + Transaction.check_quota_exn ~perm:(Connection.get_perm con) t; fct con t doms cons req.Packet.data with | Define.Invalid_path -> reply_error "EINVAL" @@ -681,9 +682,10 @@ let process_packet ~store ~cons ~doms ~con ~req = in let response = try + Transaction.check_quota_exn ~perm:(Connection.get_perm con) t; if tid <> Transaction.none then (* Remember the request and response for this operation in case we need to replay the transaction *) - Transaction.add_operation ~perm:(Connection.get_perm con) t req response; + Transaction.add_operation t req response; response with Quota.Limit_reached -> Packet.Error "EQUOTA" diff --git a/tools/ocaml/xenstored/transaction.ml b/tools/ocaml/xenstored/transaction.ml index 17b1bdf2eaf9..294143e2335b 100644 --- a/tools/ocaml/xenstored/transaction.ml +++ b/tools/ocaml/xenstored/transaction.ml @@ -85,6 +85,7 @@ type t = { oldroot: Store.Node.t; mutable paths: (Xenbus.Xb.Op.operation * Store.Path.t) list; mutable operations: (Packet.request * Packet.response) list; + mutable quota_reached: bool; mutable read_lowpath: Store.Path.t option; mutable write_lowpath: Store.Path.t option; } @@ -127,6 +128,7 @@ let make ?(internal=false) id store = oldroot = Store.get_root store; paths = []; operations = []; + quota_reached = false; read_lowpath = None; write_lowpath = None; } in @@ -143,13 +145,19 @@ let get_root t = Store.get_root t.store let is_read_only t = t.paths = [] let add_wop t ty path = t.paths <- (ty, path) :: t.paths -let add_operation ~perm t request response = +let get_operations t = List.rev t.operations + +let check_quota_exn ~perm t = if !Define.maxrequests >= 0 && not (Perms.Connection.is_dom0 perm) - && List.length t.operations >= !Define.maxrequests - then raise Quota.Limit_reached; + && (t.quota_reached || List.length t.operations >= !Define.maxrequests) + then begin + t.quota_reached <- true; + raise Quota.Limit_reached; + end + +let add_operation t request response = t.operations <- (request, response) :: t.operations -let get_operations t = List.rev t.operations let set_read_lowpath t path = t.read_lowpath <- get_lowest path t.read_lowpath let set_write_lowpath t path = t.write_lowpath <- get_lowest path t.write_lowpath -- 2.37.4