Re: [PATCH v2] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

On Fri, 2024-05-17 at 07:49 -0700, Harshit Mogalapalli wrote:
> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed.
> Fix this by reordering the kfree() post the dereference.
> 
> Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned
> systems")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

> ---
> v1->v2: Add R.B from Hans and fix commit message wrapping to 75
> chars.
> This is found by smatch and only compile tested.
> ---
>  drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git
> a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> index 7bac7841ff0a..7fa360073f6e 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct
> auxiliary_device *auxdev)
>         tpmi_sst->partition_mask_current &= ~BIT(plat_info-
> >partition);
>         /* Free the package instance when the all partitions are
> removed */
>         if (!tpmi_sst->partition_mask_current) {
> -               kfree(tpmi_sst);
>                 isst_common.sst_inst[tpmi_sst->package_id] = NULL;
> +               kfree(tpmi_sst);
>         }
>         mutex_unlock(&isst_tpmi_dev_lock);
>  }