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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@linux-foundation.org>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.