[moderation] [mm?] KCSAN: data-race in getrusage / try_to_migrate_one (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6ab41fca2e80 Merge tag 'timers-urgent-2025-09-07' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=171cc562580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=868c00f2248bb08674fe
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [Liam.H...@oracle.com ak...@linux-foundation.org da...@redhat.com harr...@oracle.com linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com ri...@surriel.com vba...@suse.cz]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/741152900af0/disk-6ab41fca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e4a5fd55ddee/vmlinux-6ab41fca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/52ae33dc3ef8/bzImage-6ab41fca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+868c00...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in getrusage / try_to_migrate_one

write to 0xffff8881036bdd58 of 8 bytes by task 4193 on cpu 1:
update_hiwater_rss include/linux/mm.h:2657 [inline]
try_to_migrate_one+0x918/0x16e0 mm/rmap.c:2455
rmap_walk_anon+0x27d/0x430 mm/rmap.c:2842
rmap_walk mm/rmap.c:2947 [inline]
try_to_migrate+0x12a/0x210 mm/rmap.c:2621
migrate_folio_unmap mm/migrate.c:1324 [inline]
migrate_pages_batch+0x6e1/0x1ae0 mm/migrate.c:1873
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 0xffff8881036bdd58 of 8 bytes by task 4194 on cpu 0:
get_mm_hiwater_rss include/linux/mm.h:2644 [inline]
setmax_mm_hiwater_rss include/linux/mm.h:2674 [inline]
getrusage+0xa52/0xbb0 kernel/sys.c:1906
io_sq_thread+0x5dd/0x1190 io_uring/sqpoll.c:320
ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000000000014fd -> 0x00000000000016c7

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4194 Comm: iou-sqp-4193 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup