[moderation] [mm?] KCSAN: data-race in folios_put_refs / need_mlock_drain (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cc3ee4ba57b7 Merge tag 'x86-urgent-2025-12-06' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164fc21a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=70709f84a6900d56
dashboard link: https://syzkaller.appspot.com/bug?extid=de65acfe4354d4b78123
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ak...@linux-foundation.org axelra...@google.com bao...@kernel.org b...@redhat.com chr...@kernel.org kas...@tencent.com linux-...@vger.kernel.org linu...@kvack.org nph...@gmail.com shik...@huaweicloud.com wei...@google.com yua...@google.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e4e4631f374/disk-cc3ee4ba.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9b3bc364e37c/vmlinux-cc3ee4ba.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6f4bd14ab533/bzImage-cc3ee4ba.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+de65ac...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in folios_put_refs / need_mlock_drain

write to 0xffff888237d27010 of 1 bytes by task 5144 on cpu 1:
folio_batch_reinit include/linux/pagevec.h:50 [inline]
folios_put_refs+0x285/0x2d0 mm/swap.c:996
folios_put include/linux/mm.h:1671 [inline]
mlock_folio_batch+0x1b5a/0x1b90 mm/mlock.c:209
munlock_folio+0xd2/0x120 mm/mlock.c:303
munlock_vma_folio mm/internal.h:1060 [inline]
__folio_remove_rmap mm/rmap.c:1762 [inline]
folio_remove_rmap_ptes+0x197/0x1a0 mm/rmap.c:1779
zap_present_folio_ptes mm/memory.c:1650 [inline]
zap_present_ptes mm/memory.c:1708 [inline]
do_zap_pte_range mm/memory.c:1810 [inline]
zap_pte_range mm/memory.c:1854 [inline]
zap_pmd_range mm/memory.c:1946 [inline]
zap_pud_range mm/memory.c:1975 [inline]
zap_p4d_range mm/memory.c:1996 [inline]
unmap_page_range+0x144c/0x2530 mm/memory.c:2017
unmap_single_vma mm/memory.c:2059 [inline]
unmap_vmas+0x23d/0x3a0 mm/memory.c:2101
exit_mmap+0x1ae/0x6b0 mm/mmap.c:1277
__mmput+0x28/0x1c0 kernel/fork.c:1130
mmput+0x40/0x50 kernel/fork.c:1153
exit_mm+0xe4/0x180 kernel/exit.c:583
do_exit+0x427/0x15d0 kernel/exit.c:961
do_group_exit+0xff/0x140 kernel/exit.c:1114
get_signal+0xe58/0xf70 kernel/signal.c:3034
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x6a/0x740 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x202/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d27010 of 1 bytes by task 32465 on cpu 0:
folio_batch_count include/linux/pagevec.h:56 [inline]
need_mlock_drain+0x30/0x50 mm/mlock.c:235
cpu_needs_drain mm/swap.c:786 [inline]
__lru_add_drain_all+0x273/0x450 mm/swap.c:877
lru_add_drain_all+0x10/0x20 mm/swap.c:893
invalidate_bdev+0x47/0x70 block/bdev.c:101
ext4_put_super+0x624/0x7d0 fs/ext4/super.c:1348
generic_shutdown_super+0xe6/0x210 fs/super.c:643
kill_block_super+0x2a/0x70 fs/super.c:1722
ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7444
deactivate_locked_super+0x75/0x1c0 fs/super.c:474
deactivate_super+0x97/0xa0 fs/super.c:507
cleanup_mnt+0x2a9/0x320 fs/namespace.c:1318
__cleanup_mnt+0x19/0x20 fs/namespace.c:1325
task_work_run+0x131/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0x1fe/0x740 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x202/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1f -> 0x11

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 32465 Comm: syz-executor Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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