On Thu, Jan 05, 2017 at 01:24:14AM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <[email protected]> > > 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. > > Reported-by: Linus Torvalds <[email protected]> > Fixes: 6b11d1d67713 ("ACPI / osl: Remove > acpi_get_table_with_size()/early_acpi_os_unmap_memory() users") > Signed-off-by: Rafael J. Wysocki <[email protected]>
Much better! Tested-by: Paul E. McKenney <[email protected]> > --- > 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; >
