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

From	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] zram: fix null dereference of handle
Date	2017-09-20 08:30 +0200
Message-ID	<urGGe-7Hy-11@gated-at.bofh.it> (permalink)
References	<urnWV-4c9-5@gated-at.bofh.it> <urGdb-7hL-1@gated-at.bofh.it>
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Hello,

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.

thanks!

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.

	-ss

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Re: [PATCH] zram: fix null dereference of handle Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-19 12:30 +0200
  BUG_ON when zsmalloc from IRQ (was zram: fix null dereference of  handle) Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-19 12:40 +0200
  Re: [PATCH] zram: fix null dereference of handle Minchan Kim <minchan@kernel.org> - 2017-09-20 08:00 +0200
    Re: [PATCH] zram: fix null dereference of handle Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-20 08:30 +0200

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