Re: [PATCH 03/17] perf, x86: Add copy_from_user_nmi_nochk for besteffort copy

[Jiri Olsa]

On Thu, Aug 02, 2012 at 11:47:30AM -0700, Andy Lutomirski wrote:
> On 07/22/2012 05:14 AM, Jiri Olsa wrote:
> > Adding copy_from_user_nmi_nochk that provides the best effort
> > copy regardless the requesting size crossing the task boundary.
> > 
> > This is going to be useful for stack dump we need in post
> > DWARF CFI based unwind, where we have predefined size of
> > the user stack to dump, and we need to store the most of
> > the requested dump size, regardless this size is crossing
> > the task boundary.
> 
> Huh?  This is a TASK_SIZE check, which makes sure that the request
> doesn't cross into kernel land.  Otherwise userspace could presumably
> read kernel memory by setting bogus values of sp.

haven't realized that..  new version won't have this

thanks,
jirka
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