[moderation] [mm?] KCSAN: data-race in mlock_folio / need_mlock_drain (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b6add54ba618 Merge tag 'pinctrl-v6.17-2' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f50634580000
kernel config: https://syzkaller.appspot.com/x/.config?x=86a2212b48ce4ce2
dashboard link: https://syzkaller.appspot.com/bug?extid=0b56a21a45d02d091d5e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [Liam.H...@oracle.com ak...@linux-foundation.org ja...@google.com linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com pfal...@suse.de vba...@suse.cz]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/94f04595632a/disk-b6add54b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/05a94af893bc/vmlinux-b6add54b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a566267f28a5/bzImage-b6add54b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0b56a2...@syzkaller.appspotmail.com

loop4: detected capacity change from 0 to 2048
EXT4-fs (loop4): failed to initialize system zone (-117)
EXT4-fs (loop4): mount failed
==================================================================
BUG: KCSAN: data-race in mlock_folio / need_mlock_drain

read-write to 0xffff888237c26a48 of 1 bytes by task 16953 on cpu 0:
folio_batch_add include/linux/pagevec.h:77 [inline]
mlock_folio+0x128/0x200 mm/mlock.c:257
mlock_vma_folio mm/internal.h:1038 [inline]
__folio_add_anon_rmap mm/rmap.c:1488 [inline]
folio_add_anon_rmap_ptes+0x20f/0x220 mm/rmap.c:1511
remove_migration_pte+0x67e/0xa70 mm/migrate.c:432
rmap_walk_anon+0x27d/0x430 mm/rmap.c:2842
rmap_walk+0x8b/0xd0 mm/rmap.c:2947
remove_migration_ptes mm/migrate.c:472 [inline]
migrate_folio_move mm/migrate.c:1388 [inline]
migrate_folios_move mm/migrate.c:1719 [inline]
migrate_pages_batch+0x1422/0x1ae0 mm/migrate.c:1966
migrate_pages_sync mm/migrate.c:1996 [inline]
migrate_pages+0xf5f/0x1770 mm/migrate.c:2105
do_mbind mm/mempolicy.c:1539 [inline]
kernel_mbind mm/mempolicy.c:1682 [inline]
__do_sys_mbind mm/mempolicy.c:1756 [inline]
__se_sys_mbind+0x975/0xac0 mm/mempolicy.c:1752
__x64_sys_mbind+0x78/0x90 mm/mempolicy.c:1752
x64_sys_call+0x2932/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:238
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237c26a48 of 1 bytes by task 16954 on cpu 1:
folio_batch_count include/linux/pagevec.h:56 [inline]
need_mlock_drain+0x30/0x50 mm/mlock.c:235
cpu_needs_drain mm/swap.c:784 [inline]
__lru_add_drain_all+0x220/0x3f0 mm/swap.c:872
lru_add_drain_all+0x10/0x20 mm/swap.c:888
invalidate_bdev+0x47/0x70 block/bdev.c:101
__ext4_fill_super fs/ext4/super.c:5703 [inline]
ext4_fill_super+0x2b5d/0x35d0 fs/ext4/super.c:5728
get_tree_bdev_flags+0x291/0x300 fs/super.c:1692
get_tree_bdev+0x1f/0x30 fs/super.c:1715
ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5760
vfs_get_tree+0x54/0x1d0 fs/super.c:1815
do_new_mount+0x207/0x5e0 fs/namespace.c:3808
path_mount+0x4a4/0xb20 fs/namespace.c:4123
do_mount fs/namespace.c:4136 [inline]
__do_sys_mount fs/namespace.c:4347 [inline]
__se_sys_mount+0x28f/0x2e0 fs/namespace.c:4324
__x64_sys_mount+0x67/0x80 fs/namespace.c:4324
x64_sys_call+0x2b4d/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16954 Comm: syz.4.4352 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.