[moderation] [mm?] KCSAN: data-race in compact_zone / compact_zone (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dcb68831eac7 Merge tag 'block-7.2-20260815' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e42679580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e71a508528491732
dashboard link: https://syzkaller.appspot.com/bug?extid=5aab5e141f425b0708fc
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [ak...@linux-foundation.org brendan...@linux.dev han...@cmpxchg.org linux-...@vger.kernel.org linu...@kvack.org mho...@suse.com sur...@google.com vba...@kernel.org z...@nvidia.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18e36a66bb95/disk-dcb68831.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c13e9fd3b099/vmlinux-dcb68831.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e6110c126236/bzImage-dcb68831.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5aab5e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in compact_zone / compact_zone

write to 0xffff88823fffa650 of 8 bytes by task 7367 on cpu 0:
update_cached_migrate mm/compaction.c:446 [inline]
isolate_migratepages mm/compaction.c:2142 [inline]
compact_zone+0x1107/0x2730 mm/compaction.c:2638
compact_zone_order mm/compaction.c:2803 [inline]
try_to_compact_pages+0x3c9/0x970 mm/compaction.c:2864
__alloc_pages_direct_compact+0x64/0x3a0 mm/page_alloc.c:4157
__alloc_pages_slowpath+0x27a/0x620 mm/page_alloc.c:4883
__alloc_frozen_pages_noprof+0x270/0x350 mm/page_alloc.c:5317
alloc_buddy_frozen_folio mm/hugetlb.c:1809 [inline]
only_alloc_fresh_hugetlb_folio+0xc9/0x1e0 mm/hugetlb.c:1849
alloc_pool_huge_folio+0x2ad/0x310 mm/hugetlb.c:1907
set_max_huge_pages mm/hugetlb.c:3825 [inline]
__nr_hugepages_store_common+0x59c/0x1070 mm/hugetlb.c:4075
hugetlb_sysctl_handler_common mm/hugetlb_sysctl.c:47 [inline]
hugetlb_sysctl_handler+0x111/0x150 mm/hugetlb_sysctl.c:57
proc_sys_call_handler+0x2ec/0x4a0 fs/proc/proc_sysctl.c:600
proc_sys_write+0x22/0x30 fs/proc/proc_sysctl.c:626
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x57d/0x990 fs/read_write.c:687
ksys_pwrite64 fs/read_write.c:794 [inline]
__do_sys_pwrite64 fs/read_write.c:802 [inline]
__se_sys_pwrite64 fs/read_write.c:799 [inline]
__x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:799
x64_sys_call+0xa2a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:19
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88823fffa650 of 8 bytes by task 32 on cpu 1:
update_cached_migrate mm/compaction.c:445 [inline]
isolate_migratepages mm/compaction.c:2142 [inline]
compact_zone+0x10e2/0x2730 mm/compaction.c:2638
kcompactd_do_work mm/compaction.c:3119 [inline]
kcompactd+0x52a/0xd80 mm/compaction.c:3213
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000095600 -> 0x0000000000095800

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 32 Comm: kcompactd0 Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================


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