syzbot

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BUG: KCSAN: data-race in block_uevent / inc_diskseq

write to 0xffff888101c8b210 of 8 bytes by task 16199 on cpu 0:
 inc_diskseq+0x2d/0x40 block/genhd.c:1583
 disk_force_media_change+0x9e/0xe0 block/disk-events.c:299
 loop_configure+0x6cb/0x9c0 drivers/block/loop.c:1055
 lo_ioctl+0x1e1/0x13a0 drivers/block/loop.c:1534
 blkdev_ioctl+0x387/0x460 block/ioctl.c:797
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888101c8b210 of 8 bytes by task 2988 on cpu 1:
 block_uevent+0x31/0x50 block/genhd.c:1320
 dev_uevent+0x360/0x3f0 drivers/base/core.c:2700
 kobject_uevent_env+0x379/0x570 lib/kobject_uevent.c:576
 kobject_synth_uevent+0x6c0/0x7f0 lib/kobject_uevent.c:207
 uevent_store+0x26/0x70 drivers/base/core.c:2773
 dev_attr_store+0x4a/0x70 drivers/base/core.c:2437
 sysfs_kf_write+0xfe/0x120 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x1df/0x2f0 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:688
 ksys_write+0xdc/0x1a0 fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:748
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000535 -> 0x0000000000000542

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2988 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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