Re: [PATCH 5.10.y] dma-buf: heaps: Fix off-by-one in CMA heap fault handler

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Sep 16, 2024 at 12:38:26AM -0700, T.J. Mercier wrote:
> On Mon, Sep 16, 2024 at 12:02 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Sep 16, 2024 at 04:34:41AM +0000, T.J. Mercier wrote:
> > > commit ea5ff5d351b520524019f7ff7f9ce418de2dad87 upstream.
> > >
> > > Until VM_DONTEXPAND was added in commit 1c1914d6e8c6 ("dma-buf: heaps:
> > > Don't track CMA dma-buf pages under RssFile") it was possible to obtain
> > > a mapping larger than the buffer size via mremap and bypass the overflow
> > > check in dma_buf_mmap_internal. When using such a mapping to attempt to
> > > fault past the end of the buffer, the CMA heap fault handler also checks
> > > the fault offset against the buffer size, but gets the boundary wrong by
> > > 1. Fix the boundary check so that we don't read off the end of the pages
> > > array and insert an arbitrary page in the mapping.
> > >
> > > Reported-by: Xingyu Jin <xingyuj@google.com>
> > > Fixes: a5d2d29e24be ("dma-buf: heaps: Move heap-helper logic into the cma_heap implementation")
> >
> > This commit is in 5.11, so why:
> >
> > > Cc: stable@vger.kernel.org # Applicable >= 5.10. Needs adjustments only for 5.10.
> >
> > does this say 5.10?
> >
> > thanks,
> >
> > greg k-h
> 
> a5d2d29e24be ("dma-buf: heaps: Move heap-helper logic into the
> cma_heap implementation") moved the code from this heap-helpers.c file
> to cma_heap.c in 5.11, which is the only place it lives upstream now.
> The bug still exists in the original location in this heap-helpers.c
> file on 5.10.

Ah, then that was the wrong Fixes: tag :(

thanks, I'll go queue this up now.

greg k-h