[PATCH v2] mm: Fix modifying of page protection by insert_pfn_pmd()

[Dan Williams]

On Wed, Apr 24, 2019 at 6:37 PM Aneesh Kumar K.V
<aneesh.kumar at linux.ibm.com> wrote:
>
> On 4/24/19 11:43 PM, Dan Williams wrote:
> > On Wed, Apr 24, 2019 at 10:38 AM Matthew Wilcox <willy at infradead.org> wrote:
> >>
> >> On Wed, Apr 24, 2019 at 10:13:15AM -0700, Dan Williams wrote:
> >>> I think unaligned addresses have always been passed to
> >>> vmf_insert_pfn_pmd(), but nothing cared until this patch. I *think*
> >>> the only change needed is the following, thoughts?
> >>>
> >>> diff --git a/fs/dax.c b/fs/dax.c
> >>> index ca0671d55aa6..82aee9a87efa 100644
> >>> --- a/fs/dax.c
> >>> +++ b/fs/dax.c
> >>> @@ -1560,7 +1560,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct
> >>> vm_fault *vmf, pfn_t *pfnp,
> >>>                  }
> >>>
> >>>                  trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
> >>> -               result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
> >>> +               result = vmf_insert_pfn_pmd(vma, pmd_addr, vmf->pmd, pfn,
> >>>                                              write);
> >>
> >> We also call vmf_insert_pfn_pmd() in dax_insert_pfn_mkwrite() -- does
> >> that need to change too?
> >
> > It wasn't clear to me that it was a problem. I think that one already
> > happens to be pmd-aligned.
> >
>
> How about vmf_insert_pfn_pud()?

That is currently not used by fsdax, only devdax, but it does seem
that it passes the unaligned fault address rather than the pud aligned
address. I'll add that to the proposed fix.