Re: [PATCH 1/3] mm/vmalloc: fix size check for remap_vmalloc_range_partial()

[Roman Penyaev]

On 2019-01-04 10:38, Michal Hocko wrote:

[...]

> > >
> > > OK, my response was more confusing than I intended. I meant to say. Is
> > > there any in kernel code that would allow the bug have had in mind?
> > > In other words can userspace trick any existing code?
> >
> > In theory any existing caller of remap_vmalloc_range() which does
> > not have an explicit size check should trigger an oops, e.g. this is
> > a good candidate:
> >
> > *** drivers/media/usb/stkwebcam/stk-webcam.c:
> > v4l_stk_mmap[789]              ret = remap_vmalloc_range(vma, 
> > sbuf->buffer,
> > 0);
>
> Hmm, sbuf->buffer is allocated in stk_setup_siobuf to have
> buf->v4lbuf.length. mmap callback maps this buffer to the vma size and
> that is indeed not enforced to be <= length AFAICS. So you are right!
>
> Can we have an example in the changelog please?

You mean to resend this particular patch with the list of possible
candidates for oops in a comment message?  Sure thing.

--
Roman