syzbot

EXT4-fs (loop7): unmounting filesystem 00000000-0000-0000-0000-000000000000.
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BUG: KCSAN: data-race in mlock_folio / need_mlock_drain

read-write to 0xffff888237d27248 of 1 bytes by task 7763 on cpu 1:
 folio_batch_add include/linux/folio_batch.h:77 [inline]
 mlock_folio+0x14d/0x240 mm/mlock.c:257
 mlock_pte_range+0x28d/0x590 mm/mlock.c:397
 walk_pmd_range mm/pagewalk.c:148 [inline]
 walk_pud_range mm/pagewalk.c:239 [inline]
 walk_p4d_range mm/pagewalk.c:280 [inline]
 walk_pgd_range+0xa76/0x1520 mm/pagewalk.c:321
 __walk_page_range+0xdd/0x340 mm/pagewalk.c:429
 walk_page_range_mm_unsafe+0x3e4/0x530 mm/pagewalk.c:525
 walk_page_range+0x56/0x70 mm/pagewalk.c:604
 mlock_vma_pages_range mm/mlock.c:449 [inline]
 mlock_fixup+0x387/0x420 mm/mlock.c:513
 apply_mlockall_flags+0x202/0x280 mm/mlock.c:740
 __do_sys_mlockall mm/mlock.c:772 [inline]
 __se_sys_mlockall+0x241/0x3c0 mm/mlock.c:751
 __x64_sys_mlockall+0x1f/0x30 mm/mlock.c:751
 x64_sys_call+0xf90/0x3020 arch/x86/include/generated/asm/syscalls_64.h:152
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d27248 of 1 bytes by task 6189 on cpu 0:
 folio_batch_count include/linux/folio_batch.h:56 [inline]
 need_mlock_drain+0x30/0x50 mm/mlock.c:235
 cpu_needs_drain mm/swap.c:792 [inline]
 __lru_add_drain_all+0x273/0x450 mm/swap.c:883
 lru_add_drain_all+0x10/0x20 mm/swap.c:899
 invalidate_bdev+0x47/0x70 block/bdev.c:101
 ext4_put_super+0x610/0x7b0 fs/ext4/super.c:1355
 generic_shutdown_super+0xee/0x220 fs/super.c:646
 kill_block_super+0x2a/0x70 fs/super.c:1725
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7492
 deactivate_locked_super+0x75/0x1c0 fs/super.c:476
 deactivate_super+0x97/0xa0 fs/super.c:509
 cleanup_mnt+0x2bb/0x330 fs/namespace.c:1312
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1319
 task_work_run+0x130/0x1a0 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:67 [inline]
 exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0a -> 0x1f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6189 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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