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]> --- 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;
