[xen staging] tools/oxenstored: Reject invalid watch paths early

[patchbot@xxxxxxx]

commit dc8caf214fb882546b0e93317b9828247a7c9da8
Author:     Edwin Török <edvin.torok@xxxxxxxxxx>
AuthorDate: Fri Jan 15 19:28:37 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Feb 4 14:17:44 2021 +0000

    tools/oxenstored: Reject invalid watch paths early
    
    Watches on invalid paths were accepted, but they would never trigger.  The
    client also got no notification that its watch is bad and would never 
trigger.
    
    Found again by the structured fuzzer, due to an error on live update reload:
    the invalid watch paths would get rejected during live update and the list 
of
    watches would be different pre/post live update.
    
    The testcase is watch on `//`, which is an invalid path.
    
    Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
    Acked-by: Christian Lindig <christian.lindig@xxxxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 tools/ocaml/xenstored/connection.ml  | 5 ++---
 tools/ocaml/xenstored/connections.ml | 4 +++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/ocaml/xenstored/connection.ml 
b/tools/ocaml/xenstored/connection.ml
index d09a0fa405..65f99ea6f2 100644
--- a/tools/ocaml/xenstored/connection.ml
+++ b/tools/ocaml/xenstored/connection.ml
@@ -158,18 +158,17 @@ let get_children_watches con path =
 let is_dom0 con =
        Perms.Connection.is_dom0 (get_perm con)
 
-let add_watch con path token =
+let add_watch con (path, apath) token =
        if !Quota.activate && !Define.maxwatch > 0 &&
           not (is_dom0 con) && con.nb_watches > !Define.maxwatch then
                raise Quota.Limit_reached;
-       let apath = get_watch_path con path in
        let l = get_watches con apath in
        if List.exists (fun w -> w.token = token) l then
                raise Define.Already_exist;
        let watch = watch_create ~con ~token ~path in
        Hashtbl.replace con.watches apath (watch :: l);
        con.nb_watches <- con.nb_watches + 1;
-       apath, watch
+       watch
 
 let del_watch con path token =
        let apath = get_watch_path con path in
diff --git a/tools/ocaml/xenstored/connections.ml 
b/tools/ocaml/xenstored/connections.ml
index 8a66eeec3a..3c7429fe7f 100644
--- a/tools/ocaml/xenstored/connections.ml
+++ b/tools/ocaml/xenstored/connections.ml
@@ -114,8 +114,10 @@ let key_of_path path =
        "" :: Store.Path.to_string_list path
 
 let add_watch cons con path token =
-       let apath, watch = Connection.add_watch con path token in
+       let apath = Connection.get_watch_path con path in
+       (* fail on invalid paths early by calling key_of_str before adding 
watch *)
        let key = key_of_str apath in
+       let watch = Connection.add_watch con (path, apath) token in
        let watches =
                if Trie.mem cons.watches key
                then Trie.find cons.watches key
--
generated by git-patchbot for /home/xen/git/xen.git#staging