Re: [Patch v3 07/13] x86/process Add arch_set_dumpable

[Thomas Gleixner]

On Thu, 18 Oct 2018, Tim Chen wrote:
> On 10/18/2018 06:28 AM, Thomas Gleixner wrote:
> > 
> > So now the obvious question. set_dumpable() operates on tsk->mm. i.e. it's
> > a process wide operation. But arch_set_dumpable() operates on the task
> > itself. What about the other tasks of that process?
> 
> I missed this part.
> 
> Fixing this is tricky as I don't see an easy way to
> reverse map mm back to all tasks that use the same mm
> to update their STIBP flags.

task is known and handed in to the function. So why do you want to reverse
map mm?

for_each_thread(task, ...) is what you want. The only thing to verify is
whether you can lock the tasks sighand lock there. And then it's enough to
set/clear the TIF bit and let it take effect at the next context switch.

Thanks,

	tglx