Re: [PATCH] mm: Fix modifying of page protection by insert_pfn()

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 27 Mar 2019 18:33:32 +0100 Jan Kara <jack@suse.cz> wrote:

> On Mon 11-03-19 10:22:44, Dan Williams wrote:
> > On Mon, Mar 11, 2019 at 1:45 AM Jan Kara <jack@suse.cz> wrote:
> > >
> > > Aneesh has reported that PPC triggers the following warning when
> > > excercising DAX code:
> > >
> > > [c00000000007610c] set_pte_at+0x3c/0x190
> > > LR [c000000000378628] insert_pfn+0x208/0x280
> > > Call Trace:
> > > [c0000002125df980] [8000000000000104] 0x8000000000000104 (unreliable)
> > > [c0000002125df9c0] [c000000000378488] insert_pfn+0x68/0x280
> > > [c0000002125dfa30] [c0000000004a5494] dax_iomap_pte_fault.isra.7+0x734/0xa40
> > > [c0000002125dfb50] [c000000000627250] __xfs_filemap_fault+0x280/0x2d0
> > > [c0000002125dfbb0] [c000000000373abc] do_wp_page+0x48c/0xa40
> > > [c0000002125dfc00] [c000000000379170] __handle_mm_fault+0x8d0/0x1fd0
> > > [c0000002125dfd00] [c00000000037a9b0] handle_mm_fault+0x140/0x250
> > > [c0000002125dfd40] [c000000000074bb0] __do_page_fault+0x300/0xd60
> > > [c0000002125dfe20] [c00000000000acf4] handle_page_fault+0x18
> > >
> > > Now that is WARN_ON in set_pte_at which is
> > >
> > >         VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
> > >
> > > The problem is that on some architectures set_pte_at() cannot cope with
> > > a situation where there is already some (different) valid entry present.
> > >
> > > Use ptep_set_access_flags() instead to modify the pfn which is built to
> > > deal with modifying existing PTE.
> > >
> > > CC: stable@vger.kernel.org
> > > Fixes: b2770da64254 "mm: add vm_insert_mixed_mkwrite()"
> > > Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
> > > Signed-off-by: Jan Kara <jack@suse.cz>
> > 
> > Acked-by: Dan Williams <dan.j.williams@intel.com>
> > 
> > Andrew, can you pick this up?
> 
> Andrew, ping?

I merged this a couple of weeks ago and it's in the queue for 5.1.