Re: [PATCH] tools/xenstored: Stash the correct request in lu_status->in

[Luca Fancellu <luca.fancellu@xxxxxxx>]

> On 1 Jul 2021, at 15:03, Julien Grall <julien@xxxxxxx> wrote:
> 
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> When Live-Updating with some load, Xenstored may hit the assert
> req->in == lu_status->in in do_lu_start().
> 
> This is happening because the request is stashed when Live-Update
> begins. This happens in a different request (see call lu_begin()
> when select the new binary) from the one performing Live-Update.
> 
> To avoid the problem, stash the request in lu_start().
> 
> Fixes: 65f19ed62aa1 ("tools/xenstore: Don't assume conn->in points to the LU 
> request")
> Reported-by: Michael Kurth <mku@xxxxxxxxxx>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Reviewed-by: luca.fancellu@xxxxxxx

> 
> ----
> 
> This was sadly missed because the on my testing the 2 requests were
> residing at the same place in memory.
> 
> This was reproduced by creating domain while Live-Updating. Without
> the patch, Xenstored will crash.
> ---
> tools/xenstore/xenstored_control.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/xenstore/xenstored_control.c 
> b/tools/xenstore/xenstored_control.c
> index a1b1bd5a718d..ff9863c17fa4 100644
> --- a/tools/xenstore/xenstored_control.c
> +++ b/tools/xenstore/xenstored_control.c
> @@ -103,7 +103,6 @@ static const char *lu_begin(struct connection *conn)
>       if (!lu_status)
>               return "Allocation failure.";
>       lu_status->conn = conn;
> -     lu_status->in = conn->in;
>       talloc_set_destructor(lu_status, lu_destroy);
> 
>       return NULL;
> @@ -757,6 +756,7 @@ static const char *lu_start(const void *ctx, struct 
> connection *conn,
>       lu_status->force = force;
>       lu_status->timeout = to;
>       lu_status->started_at = time(NULL);
> +     lu_status->in = conn->in;
> 
>       errno = delay_request(conn, conn->in, do_lu_start, conn, false);
> 
> -- 
> 2.17.1
> 
>