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commit63056e8b5eupstream. Hans reports that his mixed mode systems running v5.6-rc1 kernels hit the WARN_ON() in virt_to_phys_or_null_size(), caused by the fact that efi_guid_t objects on the vmap'ed stack happen to be misaligned with respect to their sizes. As a quick (i.e., backportable) fix, copy GUID pointer arguments to the local stack into a buffer that is naturally aligned to its size, so that it is guaranteed to cover only one physical page. Note that on x86, we cannot rely on the stack pointer being aligned the way the compiler expects, so we need to allocate an 8-byte aligned buffer of sufficient size, and copy the GUID into that buffer at an offset that is aligned to 16 bytes. Fixes:f6697df36b("x86/efi: Prevent mixed mode boot corruption with CONFIG_VMAP_STACK=y") Reported-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Hans de Goede <hdegoede@redhat.com> Cc: linux-efi@vger.kernel.org Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20200221084849.26878-2-ardb@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.