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KCSAN: data-race in __writeback_single_inode / xas_clear_mark (7)

Status: moderation: reported on 2025/05/24 21:46
Subsystems: fs mm
[Documentation on labels]
Reported-by: syzbot+39643ba03cf3a7642d40@syzkaller.appspotmail.com
First crash: 60d, last: 29d
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark (4) mm fs 6 1 1759d 1759d 0/29 auto-closed as invalid on 2020/11/02 04:03
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark (6) mm fs 6 4 139d 232d 0/29 auto-obsoleted due to no activity on 2025/05/01 12:25
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark (2) ext4 6 5 2000d 2066d 0/29 auto-closed as invalid on 2020/04/10 19:48
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark (5) fs mm 6 1 349d 349d 0/29 auto-obsoleted due to no activity on 2024/09/12 03:14
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark (3) fs mm 6 1 1795d 1795d 0/29 auto-closed as invalid on 2020/09/27 22:17
upstream KCSAN: data-race in __writeback_single_inode / xas_clear_mark ext4 6 3 2089d 2100d 0/29 closed as invalid on 2019/11/19 13:24

Sample crash report:
loop3: detected capacity change from 0 to 1024
EXT4-fs: Ignoring removed orlov option
EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
==================================================================
BUG: KCSAN: data-race in __writeback_single_inode / xas_clear_mark

write to 0xffff888106a6adfc of 4 bytes by task 3952 on cpu 1:
 xa_mark_clear lib/xarray.c:77 [inline]
 xas_clear_mark+0x16b/0x180 lib/xarray.c:932
 __folio_start_writeback+0x2ce/0x440 mm/page-writeback.c:3090
 ext4_bio_write_folio+0x5ad/0x9f0 fs/ext4/page-io.c:583
 mpage_submit_folio+0xe4/0x170 fs/ext4/inode.c:2057
 mpage_process_page_bufs+0x39b/0x4a0 fs/ext4/inode.c:2170
 mpage_prepare_extent_to_map+0x741/0xaa0 fs/ext4/inode.c:2675
 ext4_do_writepages+0xa1a/0x21c0 fs/ext4/inode.c:2861
 ext4_writepages+0x176/0x300 fs/ext4/inode.c:2953
 do_writepages+0x1c3/0x310 mm/page-writeback.c:2636
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x156/0x2c0 mm/filemap.c:794
 generic_buffers_fsync_noflush+0x45/0x120 fs/buffer.c:609
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1ab/0x690 fs/ext4/fsync.c:147
 vfs_fsync_range+0x10a/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3031 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x383/0xf00 fs/ext4/file.c:-1
 iter_file_splice_write+0x5ef/0x970 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1158
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1227
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0xb39/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:41
 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 0xffff888106a6adfc of 4 bytes by task 3943 on cpu 0:
 xa_marked include/linux/xarray.h:424 [inline]
 mapping_tagged include/linux/fs.h:542 [inline]
 __writeback_single_inode+0x1f9/0x7c0 fs/fs-writeback.c:1731
 writeback_single_inode+0x167/0x3e0 fs/fs-writeback.c:1801
 sync_inode_metadata+0x5b/0x90 fs/fs-writeback.c:2883
 generic_buffers_fsync_noflush+0xd9/0x120 fs/buffer.c:619
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1ab/0x690 fs/ext4/fsync.c:147
 vfs_fsync_range+0x10a/0x130 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3031 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x383/0xf00 fs/ext4/file.c:-1
 iter_file_splice_write+0x5ef/0x970 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1158
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1227
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0xb39/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:41
 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: 0x0e000021 -> 0x04000021

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3943 Comm: syz.3.149 Not tainted 6.16.0-rc3-syzkaller-00042-g78f4e737a53e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/24 20:23 upstream 78f4e737a53e 26d77996 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __writeback_single_inode / xas_clear_mark
2025/06/20 08:42 upstream 75f5f23f8787 ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __writeback_single_inode / xas_clear_mark
2025/06/06 07:01 upstream e271ed52b344 6b6b5f21 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __writeback_single_inode / xas_clear_mark
2025/05/25 19:26 upstream d0c22de9995b 2d4582d0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __writeback_single_inode / xas_clear_mark
2025/05/24 21:46 upstream b1427432d3b6 ed351ea7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __writeback_single_inode / xas_clear_mark
* Struck through repros no longer work on HEAD.