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Vlastimil Babka 980d059558 mm, madvise: simplify anon_name handling 
Patch series "madvise anon_name cleanups", v2.

While reviewing Lorenzo's madvise cleanups I've noticed that we can handle
anon_name in madvise code much better, so sending that as patch 1. 
Initially I wanted to do first move the existing logic from
madvise_vma_behavior() to madvise_update_vma() as a separate patch before
the actual simplification but that would require adding
anon_vma_name_put() in error handling paths only to be removed again, so
it's a single patch to avoid churn.

It's also an opportunity to move some mm code from prctl under mm, hence
patch 2.  After code moving preparation in patch 3, also unify madvise
lock handling for madvise_set_anon_name() in patch 4.


This patch (of 4):

Since the introduction in 9a10064f56 ("mm: add a field to store names
for private anonymous memory") the code to set anon_name on a vma has been
using madvise_update_vma() to call replace_anon_vma_name().  Since the
former is called also by a number of other madvise behaviours that do not
set a new anon_name, they have been passing the existing anon_name of the
vma to make replace_anon_vma_name() a no-op.

This is rather wasteful as it needs anon_vma_name_eq() to determine the
no-op situations, and checks for when replace_anon_vma_name() is allowed
(the vma is anon/shmem) duplicate the checks already done earlier in
madvise_vma_behavior().  It has also lead to commit 942341dcc5 ("mm: fix
use-after-free when anon vma name is used after vma is freed") adding
anon_name refcount get/put operations exactly to the cases that actually
do not change anon_name - just so the replace_anon_vma_name() can keep
safely determining it has nothing to do.

The recent madvise cleanups made this suboptimal handling very obvious,
but happily also allow for an easy fix.  madvise_update_vma() now has the
complete information whether it's been called to set a new anon_name, so
stop passing it the existing vma's name and doing the refcount get/put in
its only caller madvise_vma_behavior().

In madvise_update_vma() itself, limit calling of replace_anon_vma_name()
only to cases where we are setting a new name, otherwise we know it's a
no-op.  We can rely solely on the __MADV_SET_ANON_VMA_NAME behaviour and
can remove the duplicate checks for vma being anon/shmem that were done
already in madvise_vma_behavior().

Additionally, by using vma_modify_flags() when not modifying the
anon_name, avoid explicitly passing the existing vma's anon_name and
storing a pointer to it in struct madv_behavior or a local variable.  This
prevents the danger of accessing a freed anon_name after vma merging,
previously fixed by commit 942341dcc5.

Link: https://lkml.kernel.org/r/20250624-anon_name_cleanup-v2-0-600075462a11@suse.cz
Link: https://lkml.kernel.org/r/20250624-anon_name_cleanup-v2-1-600075462a11@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Colin Cross <ccross@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
History 2025-07-13 16:38:13 -07:00
arch mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() 2025-07-09 22:42:20 -07:00
block bio: use memzero_page() in bio_truncate() 2025-07-09 22:42:08 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: wp512 - Use API partial block handling 2025-06-23 16:56:56 +08:00
Documentation Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
drivers mm: remove callers of pfn_t functionality 2025-07-09 22:42:19 -07:00
fs Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
include mm/madvise: eliminate very confusing manipulation of prev VMA 2025-07-13 16:38:13 -07:00
init futex: Temporary disable FUTEX_PRIVATE_HASH 2025-07-01 15:02:05 +02:00
io_uring io_uring-6.16-20250630 2025-06-30 16:32:43 -07:00
ipc - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
kernel Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
lib Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
LICENSES LICENSES: add CC0-1.0 license text 2025-05-21 14:54:17 +02:00
mm mm, madvise: simplify anon_name handling 2025-07-13 16:38:13 -07:00
net Including fixes from Bluetooth. 2025-07-03 09:18:55 -07:00
rust Driver core fixes for 6.16-rc3 2025-06-18 14:31:16 -07:00
samples samples/damon: fix damon sample mtier for start failure 2025-07-09 21:07:55 -07:00
scripts Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
security selinux: change security_compute_sid to return the ssid or tsid on match 2025-06-19 16:13:16 -04:00
sound ALSA: hda/realtek: Fix built-in mic on ASUS VivoBook X507UAR 2025-06-26 08:02:44 +02:00
tools Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which 2025-07-12 14:48:26 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge branch 'kvm-lockdep-common' into HEAD 2025-05-28 06:29:17 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +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 MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore Python compiled bytecode 2025-04-24 10:12:46 -06:00
.mailmap 16 hotfixes. 6 are cc:stable and the remainder address post-6.15 issues 2025-06-27 20:34:10 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.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 CREDITS: Add entry for Shannon Nelson 2025-06-21 07:34:28 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS tools/mm: add script to display page state for a given PID and VADDR 2025-07-09 22:41:53 -07:00
Makefile Linux 6.16-rc5 2025-07-06 14:10:26 -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.