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KONDO KAZUMA(近藤　和真) 3cb4a48275 efi/libstub: fix efi_random_alloc() to allocate memory at alloc_min or higher address 
Following warning is sometimes observed while booting my servers:
  [    3.594838] DMA: preallocated 4096 KiB GFP_KERNEL pool for atomic allocations
  [    3.602918] swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0-1
  ...
  [    3.851862] DMA: preallocated 1024 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation

If 'nokaslr' boot option is set, the warning always happens.

On x86, ZONE_DMA is small zone at the first 16MB of physical address
space. When this problem happens, most of that space seems to be used by
decompressed kernel. Thereby, there is not enough space at DMA_ZONE to
meet the request of DMA pool allocation.

The commit 2f77465b05 ("x86/efistub: Avoid placing the kernel below
LOAD_PHYSICAL_ADDR") tried to fix this problem by introducing lower
bound of allocation.

But the fix is not complete.

efi_random_alloc() allocates pages by following steps.
1. Count total available slots ('total_slots')
2. Select a slot ('target_slot') to allocate randomly
3. Calculate a starting address ('target') to be included target_slot
4. Allocate pages, which starting address is 'target'

In step 1, 'alloc_min' is used to offset the starting address of memory
chunk. But in step 3 'alloc_min' is not considered at all.  As the
result, 'target' can be miscalculated and become lower than 'alloc_min'.

When KASLR is disabled, 'target_slot' is always 0 and the problem
happens everytime if the EFI memory map of the system meets the
condition.

Fix this problem by calculating 'target' considering 'alloc_min'.

Cc: linux-efi@vger.kernel.org
Cc: Tom Englund <tomenglund26@gmail.com>
Cc: linux-kernel@vger.kernel.org
Fixes: 2f77465b05 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR")
Signed-off-by: Kazuma Kondo <kazuma-kondo@nec.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
2024-03-22 14:08:42 +01:00
arch x86/efistub: Remap kernel text read-only before dropping NX attribute 2024-03-09 11:37:18 +01:00
block blk-iocost: Fix an UBSAN shift-out-of-bounds warning 2024-02-08 10:11:39 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: algif_hash - Remove bogus SGL free on zero-length error path 2024-02-02 18:08:12 +08:00
Documentation USB driver fixes for 6.8-rc3 2024-02-04 06:52:29 +00:00
drivers efi/libstub: fix efi_random_alloc() to allocate memory at alloc_min or higher address 2024-03-22 14:08:42 +01:00
fs 21 hotfixes. 12 are cc:stable and the remainder pertain to post-6.7 2024-02-10 15:28:07 -08:00
include efi/libstub: Add get_event_log() support for CC platforms 2024-03-09 11:37:17 +01:00
init Kconfig: Disable -Wstringop-overflow for GCC globally 2024-02-01 14:57:17 -08:00
io_uring io_uring/net: fix sr->len for IORING_OP_RECV with MSG_WAITALL and buffers 2024-02-01 06:42:36 -07:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel - Make sure a warning is issued when a hrtimer gets queued after the 2024-02-11 11:44:14 -08:00
lib linux_kselftest-kunit-fixes-6.8-rc3 2024-01-30 15:12:58 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 21 hotfixes. 12 are cc:stable and the remainder pertain to post-6.7 2024-02-10 15:28:07 -08:00
net Some fscrypt-related fixups (sparse reads are used only for encrypted 2024-02-09 17:05:02 -08:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-09 15:57:48 -08:00
scripts Kbuild fixes for v6.8 2024-02-01 11:57:42 -08:00
security lsm/stable-6.8 PR 20240131 2024-02-01 10:00:28 -08:00
sound ASoC: Fixes for v6.8 2024-02-01 19:40:42 +01:00
tools 21 hotfixes. 12 are cc:stable and the remainder pertain to post-6.7 2024-02-10 15:28:07 -08:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt Generic: 2024-01-17 13:03:37 -08:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.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 Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap MAINTAINERS: Leo Yan has moved 2024-02-07 21:20:36 -08:00
.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 MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
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 21 hotfixes. 12 are cc:stable and the remainder pertain to post-6.7 2024-02-10 15:28:07 -08:00
Makefile Linux 6.8-rc4 2024-02-11 12:18:13 -08:00
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.