Re: [PATCH] zram: fix null dereference of handle

From: Sergey Senozhatsky
Date: Wed Sep 20 2017 - 02:28:32 EST


On (09/20/17 14:51), Minchan Kim wrote:
> On Tue, Sep 19, 2017 at 07:21:25PM +0900, Sergey Senozhatsky wrote:
> > Minchan,
> >
> > I just ran across it [because I had a bug to analize where this
> > part was involved]. I'd really prefer the kernel to BUG_ON immediately
> > instead of dying in agony.
> >
> > can we, please, return BUG_ON() back?
> >
> > there is no point in trying to save the kernel once it did that type
> > of violation.
> I agree. If it happens, it would corrupt other user's buffer which ends
> up leaking some private data from others so there is pointless to keep
> system alive to debug it.


yep, I guess we are also potentially looking at __zs_map_object()
preempting zsmalloc in normal context, which would overwrite
area->vm_addr from IRQ, map it, use it, unmap it in __zs_unmap_object().
and then resumed normal context will attempt to use unmapped area->vm_addr,
I suppose.

> Do you mind sending a formal patch?

sure, will do.