lkml.org 
[lkml]   [2014]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] x86_64: A real proposal for iret-less return to kernel
On Wed, 21 May 2014, Borislav Petkov 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
> (4) it tries to send a signal to the same task
> (5) it tries to acquire sighand->siglock and loops forever

Ah, alright, but due to what mce_severity() does, this can't happen,
because if the current CPU is in the kernel (which is obviously implied by
holding a spinlock), it never proceeds sending the signal, becase
no_way_out gets set and mce_panic() invoked.

--
Jiri Kosina
SUSE Labs


\
 
 \ /
  Last update: 2014-05-22 04:21    [W:0.148 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site