> On 17 Jun 2021, at 18:38, Julien Grall <jul...@xen.org> wrote:
>
> From: Julien GralL <jgr...@amazon.com>
>
> As Live-Update is asynchronous, it is possible to receive a request to
> cancel it (either on the same connection or from a different one).
>
> Currently, this will crash xenstored because do_lu_start() assumes
> lu_status will be valid. This is not the case when Live-Update has been
> cancelled. This will result to dereference a NULL pointer and
> crash Xenstored.
>
> Rework do_lu_start() to check if lu_status is NULL and return an
> error in this case.
>
> Fixes: af216a99fb ("tools/xenstore: add the basic framework for doing the
> live update")
> Signed-off-by: Julien Grall <jgr...@amazon.com>
Reviewed-by: Luca Fancellu <luca.fance...@arm.com>
>
> ----
>
> This is currently based on top of:
>
> https://lore.kernel.org/xen-devel/20210616144324.31652-1-jul...@xen.org
>
> This can be re-ordered if necessary.
> ---
> tools/xenstore/xenstored_control.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/tools/xenstore/xenstored_control.c
> b/tools/xenstore/xenstored_control.c
> index a045f102a420..37a3d39f20b5 100644
> --- a/tools/xenstore/xenstored_control.c
> +++ b/tools/xenstore/xenstored_control.c
> @@ -696,7 +696,18 @@ static bool do_lu_start(struct delayed_request *req)
> time_t now = time(NULL);
> const char *ret;
> struct buffered_data *saved_in;
> - struct connection *conn = lu_status->conn;
> + struct connection *conn = req->data;
> +
> + /*
> + * Cancellation may have been requested asynchronously. In this
> + * case, lu_status will be NULL.
> + */
> + if (!lu_status) {
> + ret = "Cancellation was requested";
> + conn = req->data;
> + goto out;
> + } else
> + assert(lu_status->conn == conn);
>
> if (!lu_check_lu_allowed()) {
> if (now < lu_status->started_at + lu_status->timeout)
> @@ -747,7 +758,7 @@ static const char *lu_start(const void *ctx, struct
> connection *conn,
> lu_status->timeout = to;
> lu_status->started_at = time(NULL);
>
> - errno = delay_request(conn, conn->in, do_lu_start, NULL, false);
> + errno = delay_request(conn, conn->in, do_lu_start, conn, false);
>
> return NULL;
> }
> --
> 2.17.1
>
>
