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David Woodhouse 34b7abe40f x86/mm: Add _PAGE_NOPTISHADOW bit to avoid updating userspace page tables 
commit d0ceea662d upstream.

The set_p4d() and set_pgd() functions (in 4-level or 5-level page table setups
respectively) assume that the root page table is actually a 8KiB allocation,
with the userspace root immediately after the kernel root page table (so that
the former can enforce NX on on all the subordinate page tables, which are
actually shared).

However, users of the kernel_ident_mapping_init() code do not give it an 8KiB
allocation for its PGD. Both swsusp_arch_resume() and acpi_mp_setup_reset()
allocate only a single 4KiB page. The kexec code on x86_64 currently gets
away with it purely by chance, because it allocates 8KiB for its "control
code page" and then actually uses the first half for the PGD, then copies the
actual trampoline code into the second half only after the identmap code has
finished scribbling over it.

Fix this by defining a _PAGE_NOPTISHADOW bit (which can use the same bit as
_PAGE_SAVED_DIRTY since one is only for the PGD/P4D root and the other is
exclusively for leaf PTEs.). This instructs __pti_set_user_pgtbl() not to
write to the userspace 'shadow' PGD.

Strictly, the _PAGE_NOPTISHADOW bit doesn't need to be written out to the
actual page tables; since __pti_set_user_pgtbl() returns the value to be
written to the kernel page table, it could be filtered out. But there seems
to be no benefit to actually doing so.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/412c90a4df7aef077141d9f68d19cbe5602d6c6d.camel@infradead.org
Cc: stable@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-12-14 20:03:33 +01:00
arch x86/mm: Add _PAGE_NOPTISHADOW bit to avoid updating userspace page tables 2024-12-14 20:03:33 +01:00
block block: don't verify IO lock for freeze/unfreeze in elevator_init_mq() 2024-12-05 14:03:10 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-05 14:01:18 +01:00
Documentation dt-bindings: net: fec: add pps channel property 2024-12-09 10:41:11 +01:00
drivers mmc: core: Further prevent card detect during shutdown 2024-12-14 20:03:31 +01:00
fs ocfs2: update seq_file index in ocfs2_dlm_seq_next 2024-12-14 20:03:31 +01:00
include stackdepot: fix stack_depot_save_flags() in NMI context 2024-12-14 20:03:32 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring: Change res2 parameter type in io_uring_cmd_done 2024-12-14 20:03:26 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel sched/numa: fix memory leak due to the overwritten vma->numab_state 2024-12-14 20:03:32 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 20:03:32 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/mempolicy: fix migrate_to_node() assuming there is at least one VMA in a MM 2024-12-14 20:03:32 +01:00
net xsk: fix OOB map writes when deleting elements 2024-12-14 20:03:31 +01:00
rust rust: block: fix formatting of kernel::block::mq::request module 2024-12-05 14:02:21 +01:00
samples kfifo: don't include dma-mapping.h in kfifo.h 2024-12-05 14:03:03 +01:00
scripts modpost: Add .irqentry.text to OTHER_SECTIONS 2024-12-14 20:03:30 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-05 14:02:46 +01:00
sound ALSA: hda/realtek: Add support for Samsung Galaxy Book3 360 (NP730QFG) 2024-12-14 20:03:23 +01:00
tools selftest: hugetlb_dio: fix test naming 2024-12-14 20:03:27 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.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 updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -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: Remove self from DSA entry 2024-11-03 12:52:38 -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 MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile rust: allow clippy::needless_lifetimes 2024-12-14 20:03:20 +01:00
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.