linux-kernel - Re: [PATCH 3/7] x86/vm86: Move userspace accesses to do_sys

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Date:	Thu, 16 Jul 2015 12:02:06 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3/7] x86/vm86: Move userspace accesses to do_sys_vm86()

On Thu, Jul 16, 2015 at 11:42 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Thu, Jul 16, 2015 at 4:46 AM, Brian Gerst <brgerst@...il.com> wrote:
>> Move the userspace accesses down into the common function in
>> preparation for the next set of patches.
>
> Nice!
>
> Could you improve the changelog a bit? You're really changing the way
> it works (in a good way).
>
>
>> -       set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | current->thread.v86mask);
>> -       tmp = copy_vm86_regs_to_user(&current->thread.vm86_info->regs, regs);
>> -       tmp += put_user(current->thread.screen_bitmap, &current->thread.vm86_info->screen_bitmap);
>> -       if (tmp) {
>> +       set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | tsk->thread.v86mask);
>> +       user = tsk->thread.vm86_info;
>> +       put_user_try {
>
> I think that put_user_try/put_user_ex requires access_ok.
>
>
>> +       get_user_try {
>> +               unsigned short seg;
>
> This also needs access_ok, I think.

Good catch.  I modeled this off restore_sigcontext(), but the
access_ok() is actually in the caller.

--
Brian Gerst
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