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Ard Biesheuvel 2a2f9b87c4 x86/efistub: Omit physical KASLR when memory reservations exist 
commit 15aa8fb852 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-06-12 11:13:01 +02:00
arch powerpc/pseries/lparcfg: drop error message from guest name lookup 2024-06-12 11:12:59 +02:00
block blk-cgroup: Properly propagate the iostat update up the hierarchy 2024-06-12 11:12:46 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto KEYS: asymmetric: Add missing dependencies of FIPS_SIGNATURE_SELFTEST 2024-06-12 11:11:22 +02:00
Documentation dt-bindings: adc: axi-adc: add clocks property 2024-06-12 11:12:36 +02:00
drivers x86/efistub: Omit physical KASLR when memory reservations exist 2024-06-12 11:13:01 +02:00
fs kthread: add kthread_stop_put 2024-06-12 11:12:52 +02:00
include net/mlx5: Fix MTMP register capability offset in MCAM register 2024-06-12 11:12:54 +02:00
init rust: make mutually exclusive with CFI_CLANG 2024-05-02 16:32:42 +02:00
io_uring io-wq: write next_work before dropping acct_lock 2024-06-12 11:11:33 +02:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel kheaders: use command -v to test for existence of cpio 2024-06-12 11:12:58 +02:00
lib lib/test_hmm.c: handle src_pfns and dst_pfns allocation failure 2024-06-12 11:12:08 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm kthread: add kthread_stop_put 2024-06-12 11:12:52 +02:00
net net/sched: taprio: extend minimum interval restriction to entire cycle too 2024-06-12 11:12:58 +02:00
rust rust: kernel: require Send for Module implementations 2024-05-17 12:01:56 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:24:47 +01:00
scripts kconfig: fix comparison to constant symbols, 'm', 'n' 2024-06-12 11:12:58 +02:00
security KEYS: trusted: Do not use WARN when encode fails 2024-05-25 16:22:55 +02:00
sound ALSA: timer: Set lower bound of start tick time 2024-06-12 11:13:00 +02:00
tools net/sched: taprio: extend minimum interval restriction to entire cycle too 2024-06-12 11:12:58 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:28:18 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
Makefile kbuild: unify vdso_install rules 2024-06-12 11:12:32 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.