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

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Message-ID: <55DD5349.6030107@redhat.com>
Date:	Wed, 26 Aug 2015 13:48:57 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Joe Perches <joe@...ches.com>
CC:	gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, cornelia.huck@...ibm.com,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH V2 1/3] kvm: use kmalloc() instead of kzalloc() during
 iodev register/unregister



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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