[1/3] tools/oxenstored: Fix quota calculation for mkdir EEXIST

Commit Message

Andrew Cooper Feb. 3, 2021, 5:35 p.m. UTC

From: Edwin Török <[e-mail]>

We increment the domain's quota on mkdir even when the node already exists.
This results in a quota inconsistency after live update, where reconstructing
the tree from scratch results in a different quota.

Not a security issue because the domain uses up quota faster, so it will only
get a Quota error sooner than it should.

Found by the structured fuzzer.

Signed-off-by: Edwin Török <[e-mail]>
---
CC: Christian Lindig <[e-mail]>
CC: Ian Jackson <[e-mail]>
CC: Wei Liu <[e-mail]>
---
 tools/ocaml/xenstored/store.ml | 1 +
 1 file changed, 1 insertion(+)

Comments

Ian Jackson Feb. 3, 2021, 5:40 p.m. UTC | #1

Andrew Cooper writes ("[PATCH 1/3] tools/oxenstored: Fix quota calculation for mkdir EEXIST"):
> From: Edwin Török <[e-mail]>
> 
> We increment the domain's quota on mkdir even when the node already exists.
> This results in a quota inconsistency after live update, where reconstructing
> the tree from scratch results in a different quota.
> 
> Not a security issue because the domain uses up quota faster, so it will only
> get a Quota error sooner than it should.
> 
> Found by the structured fuzzer.

Thanks for these.  They look like straightforward bugfixes, so they
don't need a release ack, but FTR

Release-Acked-by: Ian Jackson <[e-mail]>

I don't feel qualified to give a maintainer-ack...

Ian.

Patch

diff --git a/tools/ocaml/xenstored/store.ml b/tools/ocaml/xenstored/store.ml
index 1bd0c81f6f..20e67b1427 100644
--- a/tools/ocaml/xenstored/store.ml
+++ b/tools/ocaml/xenstored/store.ml
@@ -419,6 +419,7 @@  let mkdir store perm path =
 	(* It's upt to the mkdir logic to decide what to do with existing path *)
 	if not (existing || (Perms.Connection.is_dom0 perm)) then Quota.check store.quota owner 0;
 	store.root <- path_mkdir store perm path;
+	if not existing then
 	Quota.add_entry store.quota owner
 
 let rm store perm path =