[moderation] [block?] KCSAN: data-race in block_uevent / inc_diskseq

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bee0e7762ad2 Merge tag 'for-linus-iommufd' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e4504ae80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ac34c1f29a8029df
dashboard link: https://syzkaller.appspot.com/bug?extid=121b850089bbda64dcd9
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/233be5f65dd2/disk-bee0e776.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/94423738a289/vmlinux-bee0e776.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b977463fa9a/bzImage-bee0e776.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+121b85...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in block_uevent / inc_diskseq

write to 0xffff888101b80620 of 8 bytes by task 22954 on cpu 0:
inc_diskseq+0x2c/0x40 block/genhd.c:1464
disk_force_media_change+0x9f/0xe0 block/disk-events.c:297
loop_configure+0x70d/0xca0 drivers/block/loop.c:1070
lo_ioctl+0x682/0x12e0
blkdev_ioctl+0x375/0x460 block/ioctl.c:633
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888101b80620 of 8 bytes by task 17775 on cpu 1:
block_uevent+0x31/0x50 block/genhd.c:1198
dev_uevent+0x2e9/0x360 drivers/base/core.c:2591
uevent_show+0x102/0x1e0 drivers/base/core.c:2647
dev_attr_show+0x39/0x90 drivers/base/core.c:2350
sysfs_kf_seq_show+0x179/0x240 fs/sysfs/file.c:59
kernfs_seq_show+0x78/0x90 fs/kernfs/file.c:205
seq_read_iter+0x2bc/0x8f0 fs/seq_file.c:230
kernfs_fop_read_iter+0xc8/0x2e0 fs/kernfs/file.c:279
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x3c0/0x590 fs/read_write.c:470
ksys_read+0xeb/0x1a0 fs/read_write.c:613
__do_sys_read fs/read_write.c:623 [inline]
__se_sys_read fs/read_write.c:621 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:621
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x000000000000152f -> 0x0000000000001530

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17775 Comm: udevd Not tainted 6.7.0-rc4-syzkaller-00009-gbee0e7762ad2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.