KCSAN: data-race in compaction_alloc / compaction_alloc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3bb61aa6 Merge tag 'arm64-fixes' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=163245c9500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=4267c44a7290ff820452
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4267c4...@syzkaller.appspotmail.com

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

write to 0xffff88813fffbc08 of 8 bytes by task 23974 on cpu 1:
update_pageblock_skip mm/compaction.c:460 [inline]
isolate_freepages mm/compaction.c:1531 [inline]
compaction_alloc+0x12a2/0x1540 mm/compaction.c:1584
unmap_and_move+0x116/0x860 mm/migrate.c:1193
migrate_pages+0x240/0xbe0 mm/migrate.c:1457
compact_zone+0x1500/0x1d30 mm/compaction.c:2318
compact_node+0xe4/0x1e0 mm/compaction.c:2594
compact_nodes mm/compaction.c:2610 [inline]
sysctl_compaction_handler+0x47/0x90 mm/compaction.c:2631
proc_sys_call_handler+0x329/0x4e0 fs/proc/proc_sysctl.c:591
proc_sys_write+0x1e/0x30 fs/proc/proc_sysctl.c:617
call_write_iter include/linux/fs.h:1903 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x6d4/0x7c0 fs/read_write.c:605
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88813fffbc08 of 8 bytes by task 23967 on cpu 0:
update_pageblock_skip mm/compaction.c:459 [inline]
isolate_freepages mm/compaction.c:1531 [inline]
compaction_alloc+0x127e/0x1540 mm/compaction.c:1584
unmap_and_move+0x116/0x860 mm/migrate.c:1193
migrate_pages+0x240/0xbe0 mm/migrate.c:1457
compact_zone+0x1500/0x1d30 mm/compaction.c:2318
compact_node+0xe4/0x1e0 mm/compaction.c:2594
compact_nodes mm/compaction.c:2610 [inline]
sysctl_compaction_handler+0x47/0x90 mm/compaction.c:2631
proc_sys_call_handler+0x329/0x4e0 fs/proc/proc_sysctl.c:591
proc_sys_write+0x1e/0x30 fs/proc/proc_sysctl.c:617
call_write_iter include/linux/fs.h:1903 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x6d4/0x7c0 fs/read_write.c:605
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23967 Comm: syz-executor.2 Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


---
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.

[syzbot]

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