Re: [PATCH 1/7] cxl/region: Fix region HPA ordering validation

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Thu, 2022-11-03 at 17:30 -0700, Dan Williams wrote:
> Some regions may not have any address space allocated. Skip them when
> validating HPA order otherwise a crash like the following may result:
> 
>  devm_cxl_add_region: cxl_acpi cxl_acpi.0: decoder3.4: created
> region9
>  BUG: kernel NULL pointer dereference, address: 0000000000000000
>  [..]
>  RIP: 0010:store_targetN+0x655/0x1740 [cxl_core]
>  [..]
>  Call Trace:
>   <TASK>
>   kernfs_fop_write_iter+0x144/0x200
>   vfs_write+0x24a/0x4d0
>   ksys_write+0x69/0xf0
>   do_syscall_64+0x3a/0x90
> 
> store_targetN+0x655/0x1740:
> alloc_region_ref at drivers/cxl/core/region.c:676
> (inlined by) cxl_port_attach_region at drivers/cxl/core/region.c:850
> (inlined by) cxl_region_attach at drivers/cxl/core/region.c:1290
> (inlined by) attach_target at drivers/cxl/core/region.c:1410
> (inlined by) store_targetN at drivers/cxl/core/region.c:1453
> 
> Cc: <stable@vger.kernel.org>
> Fixes: 384e624bb211 ("cxl/region: Attach endpoint decoders")
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/region.c |    3 +++
>  1 file changed, 3 insertions(+)

Makes sense,

Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>

> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index bb6f4fc84a3f..d26ca7a6beae 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -658,6 +658,9 @@ static struct cxl_region_ref
> *alloc_region_ref(struct cxl_port *port,
>         xa_for_each(&port->regions, index, iter) {
>                 struct cxl_region_params *ip = &iter->region->params;
>  
> +               if (!ip->res)
> +                       continue;
> +
>                 if (ip->res->start > p->res->start) {
>                         dev_dbg(&cxlr->dev,
>                                 "%s: HPA order violation %s:%pr vs
> %pr\n",
>