================================================================== BUG: KCSAN: data-race in __fat_write_inode / copy_folio_from_iter_atomic write to 0xffff88810acb307c of 4 bytes by task 7869 on cpu 0: __fat_write_inode+0x236/0x520 fs/fat/inode.c:-1 fat_write_inode+0xbf/0xd0 fs/fat/inode.c:925 write_inode fs/fs-writeback.c:1582 [inline] __writeback_single_inode+0x324/0x7c0 fs/fs-writeback.c:1802 writeback_single_inode+0x16d/0x3f0 fs/fs-writeback.c:1858 sync_inode_metadata+0x5b/0x90 fs/fs-writeback.c:2944 writeback_inode fs/fat/inode.c:1875 [inline] fat_flush_inodes+0x77/0x150 fs/fat/inode.c:1895 fat_truncate_blocks+0x4d8/0x550 fs/fat/file.c:395 fat_write_failed fs/fat/inode.c:219 [inline] fat_write_end+0xba/0x160 fs/fat/inode.c:247 generic_perform_write+0x312/0x490 mm/filemap.c:4335 __generic_file_write_iter+0xec/0x120 mm/filemap.c:4428 generic_file_write_iter+0x8d/0x2f0 mm/filemap.c:4457 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x52a/0x960 fs/read_write.c:686 ksys_write+0xda/0x1a0 fs/read_write.c:738 __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __x64_sys_write+0x40/0x50 fs/read_write.c:746 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88810acb3000 of 2048 bytes by task 27342 on cpu 1: memcpy_from_iter lib/iov_iter.c:85 [inline] iterate_bvec include/linux/iov_iter.h:123 [inline] iterate_and_advance2 include/linux/iov_iter.h:306 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:261 [inline] copy_folio_from_iter_atomic+0x760/0x1150 lib/iov_iter.c:491 generic_perform_write+0x2c2/0x490 mm/filemap.c:4332 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3490 lo_rw_aio+0x673/0x720 drivers/block/loop.c:-1 do_req_filebacked drivers/block/loop.c:-1 [inline] loop_handle_cmd drivers/block/loop.c:1926 [inline] loop_process_work+0x56d/0xaa0 drivers/block/loop.c:1961 loop_workfn+0x31/0x40 drivers/block/loop.c:1985 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340 worker_thread+0x582/0x770 kernel/workqueue.c:3421 kthread+0x489/0x510 kernel/kthread.c:463 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 27342 Comm: kworker/u8:21 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: loop2 loop_workfn ================================================================== bond0: (slave netdevsim1): Releasing backup interface bridge_slave_1: left allmulticast mode bridge_slave_1: left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state bridge_slave_0: left allmulticast mode bridge_slave_0: left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state bond0 (unregistering): (slave bond_slave_0): Releasing backup interface bond0 (unregistering): (slave bond_slave_1): Releasing backup interface bond0 (unregistering): Released all slaves bond1 (unregistering): Released all slaves bond2 (unregistering): Released all slaves bond3 (unregistering): Released all slaves bond4 (unregistering): Released all slaves hsr_slave_0: left promiscuous mode hsr_slave_1: left promiscuous mode batman_adv: batadv0: Removing interface: batadv_slave_0 batman_adv: batadv0: Removing interface: batadv_slave_1 IPVS: stop unused estimator thread 0... netdevsim netdevsim2 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 50037 - 0 netdevsim netdevsim2 netdevsim3 (unregistering): unset [1, 1] type 2 family 0 port 20002 - 0 netdevsim netdevsim2 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 50037 - 0 netdevsim netdevsim2 netdevsim2 (unregistering): unset [1, 1] type 2 family 0 port 20002 - 0 netdevsim netdevsim2 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 50037 - 0 netdevsim netdevsim2 netdevsim1 (unregistering): unset [1, 1] type 2 family 0 port 20002 - 0 netdevsim netdevsim2 »»»»»» (unregistering): unset [1, 0] type 2 family 0 port 50037 - 0 netdevsim netdevsim2 »»»»»» (unregistering): unset [1, 1] type 2 family 0 port 20002 - 0 O3ãc¤±: left allmulticast mode O3ãc¤±: left promiscuous mode bridge0: port 1(O3ãc¤±) entered disabled state bond0 (unregistering): Released all slaves bond1 (unregistering): Released all slaves bond2 (unregistering): Released all slaves bond3 (unregistering): Released all slaves bond4 (unregistering): Released all slaves bond5 (unregistering): Released all slaves bond6 (unregistering): Released all slaves bond7 (unregistering): Released all slaves $Hÿ (unregistering): (slave bond_slave_0): Releasing backup interface bond_slave_0: left promiscuous mode $Hÿ (unregistering): (slave bond_slave_1): Releasing backup interface bond_slave_1: left promiscuous mode $Hÿ (unregistering): Released all slaves bond1 (unregistering): Released all slaves bond2 (unregistering): Released all slaves bond0 (unregistering): Released all slaves bond3 (unregistering): Released all slaves bond1 (unregistering): Released all slaves bond2 (unregistering): Released all slaves bond0 (unregistering): Released all slaves bond3 (unregistering): Released all slaves bond4 (unregistering): Released all slaves bond5 (unregistering): Released all slaves tipc: Disabling bearer tipc: Left network mode hsr_slave_0: left promiscuous mode hsr_slave_1: left promiscuous mode batman_adv: batadv0: Removing interface: batadv_slave_1 batman_adv: batadv0: Removing interface: batadv_slave_0 batman_adv: batadv0: Removing interface: batadv_slave_1 hsr_slave_0: left promiscuous mode hsr_slave_1: left promiscuous mode batman_adv: batadv0: Removing interface: batadv_slave_0 batman_adv: batadv0: Removing interface: batadv_slave_1 batman_adv: batadv0: Interface deactivated: veth1_vlan batman_adv: batadv0: Removing interface: veth1_vlan team0 (unregistering): Port device team_slave_1 removed team0 (unregistering): Port device team_slave_0 removed team0 (unregistering): Port device team_slave_1 removed team0 (unregistering): Port device team_slave_0 removed team0 (unregistering): Port device team_slave_1 removed team0 (unregistering): Port device team_slave_0 removed IPVS: stop unused estimator thread 0... IPVS: stop unused estimator thread 0...