On Thu, Jan 5, 2017 at 2:24 AM, Rafael J. Wysocki <r...@rjwysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
>
> Linus reported that commit 174cc7187e6f "ACPICA: Tables: Back port
> acpi_get_table_with_size() and early_acpi_os_unmap_memory() from
> Linux kernel" added a new warning on his desktop system:
>
> ACPI Warning: Table ffffffff9fe6c0a0, Validation count is zero before
> decrement
>
> which turns out to come from the acpi_put_table() in
> detect_intel_iommu().
>
> This happens if the DMAR table is not present in which case NULL is
> passed to acpi_put_table() which doesn't check against that and
> attempts to handle it regardless.
>
> For this reason, check the pointer passed to acpi_put_table()
> before invoking it.
>
Reviewed-by: Andy Shevchenko <andy.shevche...@gmail.com>
> Reported-by: Linus Torvalds <torva...@linux-foundation.org>
> Fixes: 6b11d1d67713 ("ACPI / osl: Remove
> acpi_get_table_with_size()/early_acpi_os_unmap_memory() users")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> ---
> drivers/iommu/dmar.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> Index: linux-pm/drivers/iommu/dmar.c
> ===================================================================
> --- linux-pm.orig/drivers/iommu/dmar.c
> +++ linux-pm/drivers/iommu/dmar.c
> @@ -903,8 +903,10 @@ int __init detect_intel_iommu(void)
> x86_init.iommu.iommu_init = intel_iommu_init;
> #endif
>
> - acpi_put_table(dmar_tbl);
> - dmar_tbl = NULL;
> + if (dmar_tbl) {
> + acpi_put_table(dmar_tbl);
> + dmar_tbl = NULL;
> + }
> up_write(&dmar_global_lock);
>
> return ret ? 1 : -ENODEV;
>
--
With Best Regards,
Andy Shevchenko
