Re: [PATCH for-4.6 13/13] tools/ocaml: handle strdup failure in stub_xl_device_disk_of_vdev

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 23/07/2015 08:59, Wei Liu wrote:
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> ---
> Cc: dave.scott@eu.citrix.com
>
> Please check if the use of caml_failwith is correct.

This issue I have a different patch for, which could be 4.6 material, if
it weren't for the same issue as identified in patch 12.

In this case, Ocaml strings may contain embedded NULs which generally
makes the use of  the strxxx() functions incorrect.  OTOH, the first
thing libxl will do is assume that they are NUL terminated, so it
probably isn't too much of a problem.

There is already a dup_String_Val() function which attempts to deal with
this, although it has failure cases from integer overflows.

~Andrew

> ---
>  tools/ocaml/libs/xl/xenlight_stubs.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c b/tools/ocaml/libs/xl/xenlight_stubs.c
> index 7b8d6db..dccd7ed 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -780,6 +780,10 @@ value stub_xl_device_disk_of_vdev(value ctx, value domid, value vdev)
>  
>  	c_vdev = strdup(String_val(vdev));
>  
> +	if (!c_vdev) {
> +		caml_failwith("Failed to duplicate vdev string.");
> +	}
> +
>  	caml_enter_blocking_section();
>  	libxl_vdev_to_device_disk(CTX, c_domid, c_vdev, &c_disk);
>  	caml_leave_blocking_section();