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Re: [PATCH v2] xen: detect uninitialized xenbus in xenbus_init
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 22 Nov 2021 08:57:32 +0100
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- Cc: boris.ostrovsky@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>, stable@xxxxxxxxxxxxxxx, jgross@xxxxxxxx
- Delivery-date: Mon, 22 Nov 2021 07:58:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 19.11.2021 21:29, Stefano Stabellini wrote:
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -951,6 +951,20 @@ static int __init xenbus_init(void)
> err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> if (err)
> goto out_error;
> + /* Uninitialized. */
> + if (v == 0 || v == ULLONG_MAX) {
Didn't you have a comment in v1 here regarding the check against 0? Or was that
just like now only in the description? IOW I think there ought to be a code
comment justifying the theoretically wrong check ...
Also, while I realize there are various other similar assumptions elsewhere, I
would generally recommend to avoid such: There's no guarantee that now and
forever unsigned long long and uint64_t are the same thing. And it's easy in
cases like this one:
if (!v || !(v + 1)) {
Jan
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