From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
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 <torvalds@xxxxxxxxxxxxxxxxxxxx>
Fixes: 6b11d1d67713 ("ACPI / osl: Remove acpi_get_table_with_size()/early_acpi_os_unmap_memory() users")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
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;
--
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