5de0fef023
The EFI memory attributes code cross-references the EFI memory map with
the more granular EFI memory attributes table to ensure that they are in
sync before applying the strict permissions to the regions it describes.
Since we always install virtual mappings for the EFI runtime regions to
which these strict permissions apply, we currently perform a sanity check
on the EFI memory descriptor, and ensure that the EFI_MEMORY_RUNTIME bit
is set, and that the virtual address has been assigned.
However, in cases where a runtime region exists at physical address 0x0,
and the virtual mapping equals the physical mapping, e.g., when running
in mixed mode on x86, we encounter a memory descriptor with the runtime
attribute and virtual address 0x0, and incorrectly draw the conclusion
that a runtime region exists for which no virtual mapping was installed,
and give up altogether. The consequence of this is that firmware mappings
retain their read-write-execute permissions, making the system more
vulnerable to attacks.
So let's only bail if the virtual address of 0x0 has been assigned to a
physical region that does not reside at address 0x0.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.
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.