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[xen stable-4.12] tools/oxenstored: Reject invalid watch paths early

commit cd5666c62f9eca819eb8d89054023c703d2c9994
Author:     Edwin Török <edvin.torok@xxxxxxxxxx>
AuthorDate: Fri Jan 15 19:28:37 2021 +0000
Commit:     Ian Jackson <iwj@xxxxxxxxxxxxxx>
CommitDate: Fri Mar 19 13:46:44 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 
    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 
    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>
    (cherry picked from commit dc8caf214fb882546b0e93317b9828247a7c9da8)
 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 
index 850539e43a..daf8d804f7 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 
index 1a70d412d5..7efdf3e5e0 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#stable-4.12



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