[moderation] [block?] KCSAN: data-race in bdev_set_nr_sectors / blkdev_read_iter (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5db8752c3b81 Merge tag 'vfs-6.8.iov_iter' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d8c485e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=d7a01358d18c37d5
dashboard link: https://syzkaller.appspot.com/bug?extid=379142f5c4e45fbe6c2c
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/0636ecefd856/disk-5db8752c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc253e77814b/vmlinux-5db8752c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/63071c2b09b4/bzImage-5db8752c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+379142...@syzkaller.appspotmail.com

I/O error, dev loop4, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
==================================================================
BUG: KCSAN: data-race in bdev_set_nr_sectors / blkdev_read_iter

write to 0xffff888100630008 of 8 bytes by task 13834 on cpu 0:
bdev_set_nr_sectors+0x50/0x70 block/bdev.c:428
set_capacity block/genhd.c:61 [inline]
set_capacity_and_notify+0x6e/0x170 block/genhd.c:74
loop_set_size+0x2e/0x70 drivers/block/loop.c:237
loop_configure+0xaf9/0xca0 drivers/block/loop.c:1098
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:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888100630008 of 8 bytes by task 3478 on cpu 1:
bdev_nr_sectors include/linux/blkdev.h:769 [inline]
bdev_nr_bytes include/linux/blkdev.h:774 [inline]
blkdev_read_iter+0x58/0x2c0 block/fops.c:708
call_read_iter include/linux/fs.h:2078 [inline]
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x34c/0x480 fs/read_write.c:476
ksys_read+0xeb/0x1a0 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_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000000 -> 0x00000000000000a4

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3478 Comm: udevd Not tainted 6.7.0-syzkaller-00119-g5db8752c3b81 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================


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[syzbot]

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