Re: [RFC] x86_64: A real proposal for iret-less return to kernel

[Andy Lutomirski]

On Wed, May 21, 2014 at 2:55 PM, Borislav Petkov <bp@xxxxxxxxx> wrote:
> On Wed, May 21, 2014 at 02:52:55PM -0700, Andy Lutomirski wrote:
>> Why is it a problem if user_mode_vm(regs)?  Conversely, why is sending
>> a signal a remotely reasonable thing to do if !user_mode_vm(regs)?
>
> Let me quote Jiri:
>
> (1) task sends signal to itself
> (2) it acquires sighand->siglock so that it's able to queue the signal
> (3) MCE triggers

...and !user_mode_vm(regs), and hence we're IN_KERNEL, and we should
presumably just panic instead of trying to send a signal.

I missed the IN_KERNEL thing because I didn't realize that ->cs was
copied to struct mce.

--Andy
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