Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister

From	Jason Wang <jasowang@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister
Date	2015-08-26 07:50 +0200
Message-ID	<q1BKV-545-5@gated-at.bofh.it> (permalink)
References	<q1h9v-8th-15@gated-at.bofh.it> <q1okH-213-39@gated-at.bofh.it> <q1BBg-4SM-17@gated-at.bofh.it> <q1BKV-545-1@gated-at.bofh.it>
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On 08/26/2015 01:45 PM, Joe Perches wrote:
> On Wed, 2015-08-26 at 13:39 +0800, Jason Wang wrote:
>> > 
>> > On 08/25/2015 11:29 PM, Joe Perches wrote:
>>> > > On Tue, 2015-08-25 at 15:47 +0800, Jason Wang wrote:
>>>>> > >> > All fields of kvm_io_range were initialized or copied explicitly
>>>>> > >> > afterwards. So switch to use kmalloc().
>>> > > Is there any compiler added alignment padding
>>> > > in either structure?  If so, those padding
>>> > > areas would now be uninitialized and may leak
>>> > > kernel data if copied to user-space.
>>> > >
>> > I get your concern, but I don't a way to copy them to userspace, did you?
> I didn't look.
>
> I just wanted you to be aware there's a difference
> and a reason why kzalloc might be used even though
> all structure members are initialized.
>

I see, thanks for the reminding. Looks like we are safe and I will add
something like "kvm_io_range was never accessed by userspace" in the
commit log if there's a new version.

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[PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during iodev register/unregister Jason Wang <jasowang@redhat.com> - 2015-08-25 09:50 +0200
  Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during  iodev register/unregister Joe Perches <joe@perches.com> - 2015-08-25 17:30 +0200
    Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during  iodev register/unregister Jason Wang <jasowang@redhat.com> - 2015-08-26 07:40 +0200
      Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during  iodev register/unregister Joe Perches <joe@perches.com> - 2015-08-26 07:50 +0200
        Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during  iodev register/unregister Jason Wang <jasowang@redhat.com> - 2015-08-26 07:50 +0200

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