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Peter Xu 0b1ef4fde7 mm/debug_vm_pgtable: drop RANDOM_ORVALUE trick 
Macro RANDOM_ORVALUE was used to make sure the pgtable entry will be
populated with !none data in clear tests.

The RANDOM_ORVALUE tried to cover mostly all the bits in a pgtable entry,
even if there's no discussion on whether all the bits will be vaild.  Both
S390 and PPC64 have their own masks to avoid touching some bits.  Now it's
the turn for x86_64.

The issue is there's a recent report from Mikhail Gavrilov showing that
this can cause a warning with the newly added pte set check in commit
8430557fc5 on writable v.s.  userfaultfd-wp bit, even though the check
itself was valid, the random pte is not.  We can choose to mask more bits
out.

However the need to have such random bits setup is questionable, as now
it's already guaranteed to be true on below:

  - For pte level, the pgtable entry will be installed with value from
    pfn_pte(), where pfn points to a valid page.  Hence the pte will be
    !none already if populated with pfn_pte().

  - For upper-than-pte level, the pgtable entry should contain a directory
    entry always, which is also !none.

All the cases look like good enough to test a pxx_clear() helper.  Instead
of extending the bitmask, drop the "set random bits" trick completely.  Add
some warning guards to make sure the entries will be !none before clear().

Link: https://lkml.kernel.org/r/20240523132139.289719-1-peterx@redhat.com
Fixes: 8430557fc5 ("mm/page_table_check: support userfault wr-protect entries")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Link: https://lore.kernel.org/r/CABXGCsMB9A8-X+Np_Q+fWLURYL_0t3Y-MdoNabDM-Lzk58-DGA@mail.gmail.com
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-06-15 10:43:08 -07:00
arch mm: mmap: allow for the maximum number of bits for randomizing mmap_base by default 2024-06-15 10:43:06 -07:00
block blk-throttle: Fix incorrect display of io.max 2024-05-30 19:44:29 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation mm/memfd: add documentation for MFD_NOEXEC_SEAL MFD_EXEC 2024-06-15 10:43:07 -07:00
drivers - Convert PCI core error codes to proper error numbers since latter get 2024-06-09 08:49:13 -07:00
fs ocfs2: fix NULL pointer dereference in ocfs2_abort_trigger() 2024-06-15 10:43:04 -07:00
include mm: huge_memory: fix misused mapping_large_folio_support() for anon folios 2024-06-15 10:43:06 -07:00
init gcc: disable '-Warray-bounds' for gcc-9 2024-06-15 10:43:04 -07:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-06-04 07:39:17 -06:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel gcov: add support for GCC 14 2024-06-15 10:43:06 -07:00
lib lib/alloc_tag: do not register sysctl interface when CONFIG_SYSCTL=n 2024-06-15 10:43:05 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/debug_vm_pgtable: drop RANDOM_ORVALUE trick 2024-06-15 10:43:08 -07:00
net nfsd-6.10 fixes: 2024-06-07 15:07:57 -07:00
rust LoongArch changes for v6.10 2024-05-22 09:43:07 -07:00
samples tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
scripts Kbuild fixes for v6.10 (second) 2024-06-08 10:12:33 -07:00
security Revert "mm: init_mlocked_on_free_v3" 2024-06-15 10:43:05 -07:00
sound ALSA: seq: ump: Fix swapped song position pointer data 2024-05-31 09:51:44 +02:00
tools selftests: mm: make map_fixed_noreplace test names stable 2024-06-15 10:43:07 -07:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt The usual shower of singleton fixes and minor series all over MM, 2024-05-19 09:21:03 -07:00
.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 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 mailmap: update entry for Kees Cook 2024-05-31 08:58:36 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
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: remove Lorenzo as vmalloc reviewer 2024-06-15 10:43:05 -07:00
Makefile Linux 6.10-rc3 2024-06-09 14:19:43 -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.