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Liu Shixin c0c21293d0 mm: khugepaged: fix call hpage_collapse_scan_file() for anonymous vma 
commit f1897f2f08 upstream.

syzkaller reported such a BUG_ON():

 ------------[ cut here ]------------
 kernel BUG at mm/khugepaged.c:1835!
 Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
 ...
 CPU: 6 UID: 0 PID: 8009 Comm: syz.15.106 Kdump: loaded Tainted: G        W          6.13.0-rc6 #22
 Tainted: [W]=WARN
 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
 pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : collapse_file+0xa44/0x1400
 lr : collapse_file+0x88/0x1400
 sp : ffff80008afe3a60
 ...
 Call trace:
  collapse_file+0xa44/0x1400 (P)
  hpage_collapse_scan_file+0x278/0x400
  madvise_collapse+0x1bc/0x678
  madvise_vma_behavior+0x32c/0x448
  madvise_walk_vmas.constprop.0+0xbc/0x140
  do_madvise.part.0+0xdc/0x2c8
  __arm64_sys_madvise+0x68/0x88
  invoke_syscall+0x50/0x120
  el0_svc_common.constprop.0+0xc8/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x34/0x128
  el0t_64_sync_handler+0xc8/0xd0
  el0t_64_sync+0x190/0x198

This indicates that the pgoff is unaligned.  After analysis, I confirm the
vma is mapped to /dev/zero.  Such a vma certainly has vm_file, but it is
set to anonymous by mmap_zero().  So even if it's mmapped by 2m-unaligned,
it can pass the check in thp_vma_allowable_order() as it is an
anonymous-mmap, but then be collapsed as a file-mmap.

It seems the problem has existed for a long time, but actually, since we
have khugepaged_max_ptes_none check before, we will skip collapse it as it
is /dev/zero and so has no present page.  But commit d8ea7cc854 limit
the check for only khugepaged, so the BUG_ON() can be triggered by
madvise_collapse().

Add vma_is_anonymous() check to make such vma be processed by
hpage_collapse_scan_pmd().

Link: https://lkml.kernel.org/r/20250111034511.2223353-1-liushixin2@huawei.com
Fixes: d8ea7cc854 ("mm/khugepaged: add flag to predicate khugepaged-only behavior")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mattew Wilcox <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[acsjakub: backport, clean apply]
Signed-off-by: Jakub Acs <acsjakub@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-08-01 09:48:47 +01:00
arch KVM: x86: Free vCPUs before freeing VM state 2025-08-01 09:48:47 +01:00
block block: fix kobject leak in blk_unregister_queue 2025-07-24 08:56:30 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP() 2025-07-17 18:37:24 +02:00
Documentation bpf: Adjust free target to avoid global starvation of LRU map 2025-07-17 18:37:22 +02:00
drivers Revert "drm/xe/forcewake: Add a helper xe_force_wake_ref_has_domain()" 2025-08-01 09:48:47 +01:00
fs ext4: fix out of bounds punch offset 2025-08-01 09:48:46 +01:00
include sprintf.h requires stdarg.h 2025-08-01 09:48:43 +01:00
init rust: clean Rust 1.88.0's unnecessary_transmutes lint 2025-05-18 08:24:51 +02:00
io_uring io_uring/poll: fix POLLERR handling 2025-07-24 08:56:23 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel selftests/bpf: Add tests with stack ptr register in conditional jmp 2025-08-01 09:48:44 +01:00
lib lib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users() 2025-07-17 18:37:14 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: khugepaged: fix call hpage_collapse_scan_file() for anonymous vma 2025-08-01 09:48:47 +01:00
net net/sched: sch_qfq: Avoid triggering might_sleep in atomic context in qfq_delete_class 2025-08-01 09:48:41 +01:00
rust rust: use #[used(compiler)] to fix build and modpost with Rust >= 1.89.0 2025-07-24 08:56:37 +02:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-05-29 11:02:01 +02:00
scripts rust: use #[used(compiler)] to fix build and modpost with Rust >= 1.89.0 2025-07-24 08:56:37 +02:00
security selinux: change security_compute_sid to return the ssid or tsid on match 2025-07-10 16:05:04 +02:00
sound ALSA: hda: Add missing NVIDIA HDA codec IDs 2025-08-01 09:48:47 +01:00
tools selftests/bpf: Add tests with stack ptr register in conditional jmp 2025-08-01 09:48:44 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.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 rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.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 Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.40 2025-07-24 08:56:38 +02:00
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.