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Re: [Xen-devel] [PATCH] fix misc issues related to allowingsupport of more CPUs

  • To: Jan Beulich <jbeulich@xxxxxxxxxx>
  • From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Date: Mon, 22 Sep 2008 09:35:21 +0100
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 22 Sep 2008 01:35:46 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AckcjiZIZLxHkIiBEd2psAAX8io7RQ==
  • Thread-topic: [Xen-devel] [PATCH] fix misc issues related to allowingsupport of more CPUs

On 22/9/08 08:46, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> Why must it be WARN_ON()? You think you could specify strings so long that
>> they overflow 32 bits? You've got other problems in that case.
> No, that's not the reason. It's because of how bitmap_scnprintf() and
> bitmap_scnlistprintf() work - they can (validly, assuming that the code
> having been derived from Linux and still being that way in Linux, hence
> apparently considered correct) pass negative sizes to scnprintf(), and
> hence it must not kill the system to actually do so.

The obvious answer would be to fix the bogus callers. Or consider negative
size to be a valid input. Warning on what callers consider valid behaviour
is just weird. I would say the former (fix the callers) is the better way to
go here; presumably they just need to clamp the size parameter.

 -- Keir

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