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Ricardo Cañuelo Navarro ff673b71f0 mm,madvise,hugetlb: check for 0-length range after end address adjustment 
commit 2ede647a6f upstream.

Add a sanity check to madvise_dontneed_free() to address a corner case in
madvise where a race condition causes the current vma being processed to
be backed by a different page size.

During a madvise(MADV_DONTNEED) call on a memory region registered with a
userfaultfd, there's a period of time where the process mm lock is
temporarily released in order to send a UFFD_EVENT_REMOVE and let
userspace handle the event.  During this time, the vma covering the
current address range may change due to an explicit mmap done concurrently
by another thread.

If, after that change, the memory region, which was originally backed by
4KB pages, is now backed by hugepages, the end address is rounded down to
a hugepage boundary to avoid data loss (see "Fixes" below).  This rounding
may cause the end address to be truncated to the same address as the
start.

Make this corner case follow the same semantics as in other similar cases
where the requested region has zero length (ie.  return 0).

This will make madvise_walk_vmas() continue to the next vma in the range
(this time holding the process mm lock) which, due to the prev pointer
becoming stale because of the vma change, will be the same hugepage-backed
vma that was just checked before.  The next time madvise_dontneed_free()
runs for this vma, if the start address isn't aligned to a hugepage
boundary, it'll return -EINVAL, which is also in line with the madvise
api.

From userspace perspective, madvise() will return EINVAL because the start
address isn't aligned according to the new vma alignment requirements
(hugepage), even though it was correctly page-aligned when the call was
issued.

Link: https://lkml.kernel.org/r/20250203075206.1452208-1-rcn@igalia.com
Fixes: 8ebe0a5eaa ("mm,madvise,hugetlb: fix unexpected data loss with MADV_DONTNEED on hugetlbfs")
Signed-off-by: Ricardo Cañuelo Navarro <rcn@igalia.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Florent Revest <revest@google.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-02-27 04:30:23 -08:00
arch s390/boot: Fix ESSA detection 2025-02-27 04:30:22 -08:00
block partitions: mac: fix handling of bogus partition table 2025-02-21 14:01:36 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix boot-up self-test race 2025-02-08 09:57:28 +01:00
Documentation strparser: Add read_sock callback 2025-02-27 04:30:19 -08:00
drivers gve: set xdp redirect target only when it is available 2025-02-27 04:30:22 -08:00
fs smb: client: fix chmod(2) regression with ATTR_READONLY 2025-02-27 04:30:22 -08:00
include bpf: Fix wrong copied_seq calculation 2025-02-27 04:30:19 -08:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring: prevent opcode speculation 2025-02-27 04:30:21 -08:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel acct: block access to kernel internal filesystems 2025-02-27 04:30:23 -08:00
lib lib/iov_iter: fix import_iovec_ubuf iovec management 2025-02-27 04:30:22 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm,madvise,hugetlb: check for 0-length range after end address adjustment 2025-02-27 04:30:23 -08:00
net drop_monitor: fix incorrect initialization order 2025-02-27 04:30:21 -08:00
rust rust: kbuild: add -fzero-init-padding-bits to bindgen_skip_cflags 2025-02-21 14:01:39 +01:00
samples samples/landlock: Fix possible NULL dereference in parse_path() 2025-02-08 09:57:11 +01:00
scripts kbuild: Use -fzero-init-padding-bits=all 2025-02-21 14:01:27 +01:00
security KEYS: trusted: dcp: fix improper sg use with CONFIG_VMAP_STACK=y 2025-02-17 10:05:09 +01:00
sound ASoC: SOF: pcm: Clear the susbstream pointer to NULL on close 2025-02-27 04:30:23 -08:00
tools selftests/bpf: Add tests for raw_tp null handling 2025-02-27 04:30:19 -08:00
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 Linux 6.12.16 2025-02-21 14:01:47 +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.