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BUG: KCSAN: data-race in __xa_clear_mark / xas_find_marked

read-write to 0xffff888107bb9b48 of 8 bytes by interrupt on cpu 1:
 instrument_read_write include/linux/instrumented.h:56 [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:2100
 __folio_end_writeback+0xf4/0x360 mm/page-writeback.c:2969
 folio_end_writeback_no_dropbehind+0x6d/0x1d0 mm/filemap.c:1666
 folio_end_writeback+0x1c/0x70 mm/filemap.c:1692
 ext4_finish_bio+0x459/0x8b0 fs/ext4/page-io.c:145
 ext4_end_bio+0x27b/0x380 fs/ext4/page-io.c:393
 bio_endio+0x38a/0x420 block/bio.c:1792
 blk_update_request+0x338/0x740 block/blk-mq.c:1016
 scsi_end_request+0x53/0x4c0 drivers/scsi/scsi_lib.c:647
 scsi_io_completion+0x7f/0x1d0 drivers/scsi/scsi_lib.c:1088
 scsi_finish_command+0x1c7/0x1e0 drivers/scsi/scsi.c:198
 scsi_complete+0x155/0x4f0 drivers/scsi/scsi_lib.c:1568
 blk_complete_reqs block/blk-mq.c:1253 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1258
 handle_softirqs+0xb9/0x2a0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x39/0xc0 kernel/softirq.c:723
 common_interrupt+0x83/0x90 arch/x86/kernel/irq.c:326
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
 is_atomic kernel/kcsan/core.c:249 [inline]
 should_watch kernel/kcsan/core.c:277 [inline]
 check_access kernel/kcsan/core.c:752 [inline]
 __tsan_read8+0xe8/0x190 kernel/kcsan/core.c:1025
 ensure_safe_net_sysctl net/sysctl_net.c:144 [inline]
 register_net_sysctl_sz+0x93/0x1c0 net/sysctl_net.c:169
 __addrconf_sysctl_register+0x240/0x340 net/ipv6/addrconf.c:7327
 addrconf_sysctl_register+0xe6/0x130 net/ipv6/addrconf.c:7375
 ipv6_add_dev+0x8a2/0xac0 net/ipv6/addrconf.c:459
 addrconf_notify+0x4a5/0x8f0 net/ipv6/addrconf.c:3654
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x83/0x1c0 kernel/notifier.c:453
 call_netdevice_notifiers_info net/core/dev.c:2249 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers+0xb5/0x110 net/core/dev.c:2301
 register_netdevice+0xe30/0x1000 net/core/dev.c:11479
 register_netdev+0x3b/0x50 net/core/dev.c:11557
 ip6gre_init_net+0x233/0x2e0 net/ipv6/ip6_gre.c:1608
 ops_init+0x22a/0x2e0 net/core/net_namespace.c:137
 setup_net+0x9f/0x230 net/core/net_namespace.c:446
 copy_net_ns+0x310/0x450 net/core/net_namespace.c:579
 create_new_namespaces+0x20e/0x440 kernel/nsproxy.c:130
 unshare_nsproxy_namespaces+0xe6/0x120 kernel/nsproxy.c:226
 ksys_unshare+0x3f2/0x6f0 kernel/fork.c:3173
 __do_sys_unshare kernel/fork.c:3244 [inline]
 __se_sys_unshare kernel/fork.c:3242 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3242
 x64_sys_call+0x1cef/0x3020 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107bb9b48 of 8 bytes by task 17264 on cpu 0:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 find_get_entry mm/filemap.c:2069 [inline]
 filemap_get_folios_tag+0xfa/0x510 mm/filemap.c:2337
 __filemap_fdatawait_range mm/filemap.c:523 [inline]
 filemap_fdatawait_keep_errors+0x6c/0x190 mm/filemap.c:626
 wait_sb_inodes fs/fs-writeback.c:2812 [inline]
 sync_inodes_sb+0x424/0x4d0 fs/fs-writeback.c:2945
 sync_inodes_one_sb+0x3d/0x50 fs/sync.c:77
 __iterate_supers+0x110/0x220 fs/super.c:927
 iterate_supers+0x1f/0x30 fs/super.c:942
 ksys_sync fs/sync.c:102 [inline]
 __ia32_sys_sync+0x5c/0xb0 fs/sync.c:111
 x64_sys_call+0x2f3a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffe000000000000 -> 0xc000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 17264 Comm: syz.4.4806 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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