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Ard Biesheuvel 15aa8fb852 x86/efistub: Omit physical KASLR when memory reservations exist 
The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

  a1b87d54f4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc:  <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
History 2024-05-17 17:06:18 +02:00
arch EFI fixes for v6.9 #2 2024-03-24 13:54:06 -07:00
block vfs-6.9-rc1.fixes 2024-03-18 09:15:50 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
Documentation Documentation: Mark the 'efivars' sysfs interface as removed 2024-04-13 10:33:02 +02:00
drivers x86/efistub: Omit physical KASLR when memory reservations exist 2024-05-17 17:06:18 +02:00
fs efi: Clear up misconceptions about a maximum variable name size 2024-04-13 10:33:02 +02:00
include efi: Clear up misconceptions about a maximum variable name size 2024-04-13 10:33:02 +02:00
init RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
io_uring io_uring/sqpoll: early exit thread if task_context wasn't allocated 2024-03-18 20:22:42 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel dma-mapping fixes for Linux 6.9 2024-03-24 10:45:31 -07:00
lib hardening fixes for v6.9-rc1 2024-03-23 08:43:21 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
net Including fixes from CAN, netfilter, wireguard and IPsec. 2024-03-21 14:50:39 -07:00
rust Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts LoongArch changes for v6.9 2024-03-22 10:22:45 -07:00
security - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
sound sound fixes #2 for 6.9-rc2 2024-03-22 09:44:19 -07:00
tools RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM Xen and pfncache changes for 6.9: 2024-03-11 10:42:55 -04:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap Char/Misc and other driver subsystem updates for 6.9-rc1 2024-03-21 13:21:31 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Not a ton of stuff happening in the clk framework in this pull request. We got 2024-03-15 11:48:01 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS RISC-V Patches for the 6.9 Merge Window 2024-03-22 10:41:13 -07:00
Makefile Linux 6.9-rc1 2024-03-24 14:10:05 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.