syzbot

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BUG: KCSAN: data-race in block_uevent / inc_diskseq

write to 0xffff88810214d218 of 8 bytes by task 9194 on cpu 0:
 inc_diskseq+0x2d/0x40 block/genhd.c:1583
 disk_force_media_change+0x9e/0xe0 block/disk-events.c:297
 loop_configure+0x6cb/0x9c0 drivers/block/loop.c:1056
 lo_ioctl+0x1e1/0x13a0 drivers/block/loop.c:1555
 blkdev_ioctl+0x387/0x460 block/ioctl.c:792
 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+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810214d218 of 8 bytes by task 3002 on cpu 1:
 block_uevent+0x31/0x50 block/genhd.c:1320
 dev_uevent+0x375/0x400 drivers/base/core.c:2700
 uevent_show+0x11a/0x200 drivers/base/core.c:2756
 dev_attr_show+0x3f/0xa0 drivers/base/core.c:2421
 sysfs_kf_seq_show+0x1a3/0x280 fs/sysfs/file.c:65
 kernfs_seq_show+0x82/0xa0 fs/kernfs/file.c:223
 seq_read_iter+0x31e/0x940 fs/seq_file.c:230
 kernfs_fop_read_iter+0xc1/0x330 fs/kernfs/file.c:297
 new_sync_read fs/read_write.c:491 [inline]
 vfs_read+0x6c0/0x7f0 fs/read_write.c:572
 ksys_read+0xdc/0x1a0 fs/read_write.c:715
 __do_sys_read fs/read_write.c:724 [inline]
 __se_sys_read fs/read_write.c:722 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:722
 x64_sys_call+0x2889/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000020b -> 0x0000000000000219

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3002 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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