Re: [PATCH v3 3/5] libnvdimm/namespace: Enforce memremap_compat_align()

[Dan Williams]

On Mon, Mar 2, 2020 at 4:09 AM Aneesh Kumar K.V
<aneesh.kumar@xxxxxxxxxxxxx> wrote:
>
> Dan Williams <dan.j.williams@xxxxxxxxx> writes:
>
> > The pmem driver on PowerPC crashes with the following signature when
> > instantiating misaligned namespaces that map their capacity via
> > memremap_pages().
> >
> >     BUG: Unable to handle kernel data access at 0xc001000406000000
> >     Faulting instruction address: 0xc000000000090790
> >     NIP [c000000000090790] arch_add_memory+0xc0/0x130
> >     LR [c000000000090744] arch_add_memory+0x74/0x130
> >     Call Trace:
> >      arch_add_memory+0x74/0x130 (unreliable)
> >      memremap_pages+0x74c/0xa30
> >      devm_memremap_pages+0x3c/0xa0
> >      pmem_attach_disk+0x188/0x770
> >      nvdimm_bus_probe+0xd8/0x470
> >
> > With the assumption that only memremap_pages() has alignment
> > constraints, enforce memremap_compat_align() for
> > pmem_should_map_pages(), nd_pfn, and nd_dax cases. This includes
> > preventing the creation of namespaces where the base address is
> > misaligned and cases there infoblock padding parameters are invalid.
> >
>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
>
> > Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> > Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
> > Fixes: a3619190d62e ("libnvdimm/pfn: stop padding pmem namespaces to section alignment")
> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > ---
> >  drivers/nvdimm/namespace_devs.c |   12 ++++++++++++
> >  drivers/nvdimm/pfn_devs.c       |   26 +++++++++++++++++++++++---
> >  2 files changed, 35 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
> > index 032dc61725ff..68e89855f779 100644
> > --- a/drivers/nvdimm/namespace_devs.c
> > +++ b/drivers/nvdimm/namespace_devs.c
> > @@ -10,6 +10,7 @@
> >  #include <linux/nd.h>
> >  #include "nd-core.h"
> >  #include "pmem.h"
> > +#include "pfn.h"
> >  #include "nd.h"
> >
> >  static void namespace_io_release(struct device *dev)
> > @@ -1739,6 +1740,17 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
> >               return ERR_PTR(-ENODEV);
> >       }
>
> May be add a comment here that both dax/fsdax namespace details are
> checked in nd_pfn_validate() so that we look at start_pad and end_trunc
> while validating the namespace?
>
> >
> > +     if (pmem_should_map_pages(dev)) {
> > +             struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
> > +             struct resource *res = &nsio->res;
> > +
> > +             if (!IS_ALIGNED(res->start | (res->end + 1),
> > +                                     memremap_compat_align())) {
> > +                     dev_err(&ndns->dev, "%pr misaligned, unable to map\n", res);
> > +                     return ERR_PTR(-EOPNOTSUPP);
> > +             }
> > +     }
> > +
> >       if (is_namespace_pmem(&ndns->dev)) {
> >               struct nd_namespace_pmem *nspm;
> >
> > diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> > index 79fe02d6f657..3bdd4b883d05 100644
> > --- a/drivers/nvdimm/pfn_devs.c
> > +++ b/drivers/nvdimm/pfn_devs.c
> > @@ -446,6 +446,7 @@ static bool nd_supported_alignment(unsigned long align)
> >  int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
> >  {
> >       u64 checksum, offset;
> > +     struct resource *res;
> >       enum nd_pfn_mode mode;
> >       struct nd_namespace_io *nsio;
> >       unsigned long align, start_pad;
> > @@ -578,13 +579,14 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
> >        * established.
> >        */
> >       nsio = to_nd_namespace_io(&ndns->dev);
> > -     if (offset >= resource_size(&nsio->res)) {
> > +     res = &nsio->res;
> > +     if (offset >= resource_size(res)) {
> >               dev_err(&nd_pfn->dev, "pfn array size exceeds capacity of %s\n",
> >                               dev_name(&ndns->dev));
> >               return -EOPNOTSUPP;
> >       }
> >
> > -     if ((align && !IS_ALIGNED(nsio->res.start + offset + start_pad, align))
> > +     if ((align && !IS_ALIGNED(res->start + offset + start_pad, align))
> >                       || !IS_ALIGNED(offset, PAGE_SIZE)) {
> >               dev_err(&nd_pfn->dev,
> >                               "bad offset: %#llx dax disabled align: %#lx\n",
> > @@ -592,6 +594,18 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
> >               return -EOPNOTSUPP;
> >       }
> >
> > +     if (!IS_ALIGNED(res->start + le32_to_cpu(pfn_sb->start_pad),
> > +                             memremap_compat_align())) {
> > +             dev_err(&nd_pfn->dev, "resource start misaligned\n");
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     if (!IS_ALIGNED(res->end + 1 - le32_to_cpu(pfn_sb->end_trunc),
> > +                             memremap_compat_align())) {
> > +             dev_err(&nd_pfn->dev, "resource end misaligned\n");
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> >       return 0;
> >  }
> >  EXPORT_SYMBOL(nd_pfn_validate);
> > @@ -750,7 +764,13 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
> >       start = nsio->res.start;
> >       size = resource_size(&nsio->res);
> >       npfns = PHYS_PFN(size - SZ_8K);
> > -     align = max(nd_pfn->align, SUBSECTION_SIZE);
> > +     align = max(nd_pfn->align, memremap_compat_align());
> > +     if (!IS_ALIGNED(start, memremap_compat_align())) {
> > +             dev_err(&nd_pfn->dev, "%s: start %pa misaligned to %#lx\n",
> > +                             dev_name(&ndns->dev), &start,
> > +                             memremap_compat_align());
> > +             return -EINVAL;
> > +     }
>
> This validates start in case of a new namespace creation where the user
> updated nd_region->align value? A comment there would help when looking
> at the code later?

Yeah, sounds good will respin with those updates.