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upstream test error: KCSAN: data-race in __xa_clear_mark / xas_find_marked (3)

Status: moderation: reported on 2025/04/30 08:05
Subsystems: mm fs
[Documentation on labels]
Reported-by: syzbot+059bc69d4ad4a1169f0b@syzkaller.appspotmail.com
First crash: 4d02h, last: 4d02h
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream upstream test error: KCSAN: data-race in __xa_clear_mark / xas_find_marked fs mm 2 287d 314d 0/28 auto-obsoleted due to no activity on 2024/08/24 21:02
upstream upstream test error: KCSAN: data-race in __xa_clear_mark / xas_find_marked (2) fs mm 1 161d 161d 0/28 auto-obsoleted due to no activity on 2025/01/18 12:40

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff888106ce1900 of 8 bytes by task 37 on cpu 0:
 instrument_read_write include/linux/instrumented.h:55 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:114 [inline]
 node_clear_mark lib/xarray.c:102 [inline]
 xas_clear_mark lib/xarray.c:922 [inline]
 __xa_clear_mark+0xf5/0x1e0 lib/xarray.c:2094
 __folio_end_writeback+0x177/0x470 mm/page-writeback.c:3047
 folio_end_writeback+0xb6/0x3a0 mm/filemap.c:1648
 ext4_finish_bio+0x459/0x8c0 fs/ext4/page-io.c:144
 ext4_release_io_end+0x9f/0x1f0 fs/ext4/page-io.c:159
 ext4_end_io_end+0x18d/0x240 fs/ext4/page-io.c:210
 ext4_do_flush_completed_IO fs/ext4/page-io.c:287 [inline]
 ext4_end_io_rsv_work+0x151/0x1e0 fs/ext4/page-io.c:302
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888106ce1900 of 8 bytes by task 3457 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1746 [inline]
 xas_find_marked+0x218/0x620 lib/xarray.c:1510
 find_get_entry+0x5d/0x380 mm/filemap.c:2027
 filemap_get_folios_tag+0x13b/0x210 mm/filemap.c:2295
 __filemap_fdatawait_range mm/filemap.c:530 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x180 mm/filemap.c:633
 wait_sb_inodes fs/fs-writeback.c:2714 [inline]
 sync_inodes_sb+0x39c/0x440 fs/fs-writeback.c:2836
 sync_inodes_one_sb+0x3d/0x50 fs/sync.c:77
 iterate_supers+0xa2/0x140 fs/super.c:934
 ksys_sync+0x5c/0xe0 fs/sync.c:102
 __ia32_sys_sync+0xe/0x20 fs/sync.c:113
 x64_sys_call+0x2e53/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffff00000000000 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3457 Comm: syz.2.148 Not tainted 6.15.0-rc4-syzkaller-00042-gb6ea1680d0ac #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/04/30 08:05 upstream b6ea1680d0ac 85a5a23f .config console log report [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce upstream test error: KCSAN: data-race in __xa_clear_mark / xas_find_marked
* Struck through repros no longer work on HEAD.