syzbot

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BUG: KCSAN: data-race in block_uevent / inc_diskseq

write to 0xffff888101ed2e20 of 8 bytes by task 5297 on cpu 1:
 inc_diskseq+0x2c/0x40 block/genhd.c:1469
 disk_force_media_change+0x9f/0xf0 block/disk-events.c:297
 __loop_clr_fd+0x270/0x3f0 drivers/block/loop.c:1170
 loop_clr_fd drivers/block/loop.c:1253 [inline]
 lo_ioctl+0xea6/0x1330 drivers/block/loop.c:1555
 blkdev_ioctl+0x37f/0x470 block/ioctl.c:640
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0xd3/0x150 fs/ioctl.c:890
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

read to 0xffff888101ed2e20 of 8 bytes by task 3572 on cpu 0:
 block_uevent+0x31/0x50 block/genhd.c:1201
 dev_uevent+0x2f3/0x380 drivers/base/core.c:2605
 uevent_show+0x10c/0x1f0 drivers/base/core.c:2661
 dev_attr_show+0x3a/0xa0 drivers/base/core.c:2364
 sysfs_kf_seq_show+0x17c/0x250 fs/sysfs/file.c:59
 kernfs_seq_show+0x7c/0x90 fs/kernfs/file.c:205
 seq_read_iter+0x2d7/0x940 fs/seq_file.c:230
 kernfs_fop_read_iter+0xc6/0x310 fs/kernfs/file.c:279
 call_read_iter include/linux/fs.h:2102 [inline]
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x5bc/0x6b0 fs/read_write.c:476
 ksys_read+0xeb/0x1b0 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:627
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

value changed: 0x000000000000023c -> 0x000000000000023f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3572 Comm: udevd Not tainted 6.8.0-syzkaller-08073-g480e035fc4c7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
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I/O error, dev loop3, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
I/O error, dev loop1, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
I/O error, dev loop2, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
I/O error, dev loop3, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
I/O error, dev loop3, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
Buffer I/O error on dev loop3, logical block 0, async page read
I/O error, dev loop3, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0