Commit 696c7f8e authored Jan 05, 2017 by Rafael J. Wysocki

ACPI / DMAR: Avoid passing NULL to acpi_put_table()



Linus reported that commit 174cc718 "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 <torvalds@linux-foundation.org>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Fixes: 6b11d1d6 ("ACPI / osl: Remove acpi_get_table_with_size()/early_acpi_os_unmap_memory() users")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 0c744ea4

drivers/iommu/dmar.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -903,8 +903,10 @@ int __init detect_intel_iommu(void)
		x86_init.iommu.iommu_init = intel_iommu_init;
		#endif

		if (dmar_tbl) {
		acpi_put_table(dmar_tbl);
		dmar_tbl = NULL;
		}
		up_write(&dmar_global_lock);

		return ret ? 1 : -ENODEV;

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