| 0/0 |
2026/03/06 00:00 |
flow |
repro |
3m
Results: map[ReproOpts:{
"threaded": true,
"repeat": true,
"procs": 1
} ReproSyz:r0 = syz_mount_image$vfat(&(0x7f0000000000)='vfat\x00', &(0x7f0000000100)='./mnt\x00', 0x0, 0x0, 0x0, 0x0, 0x0)
r1 = openat(AT_FDCWD, &(0x7f0000000200)='./mnt/file0\x00', 0x42, 0x1ff)
r2 = openat(AT_FDCWD, &(0x7f0000000300)='/dev/loop0\x00', 0x0, 0x0)
r3 = openat(AT_FDCWD, &(0x7f0000000320)='/dev/loop1\x00', 0x0, 0x0)
r4 = openat(AT_FDCWD, &(0x7f0000000340)='/dev/loop2\x00', 0x0, 0x0)
r5 = openat(AT_FDCWD, &(0x7f0000000360)='/dev/loop3\x00', 0x0, 0x0)
r6 = openat(AT_FDCWD, &(0x7f0000000380)='/dev/loop4\x00', 0x0, 0x0)
r7 = openat(AT_FDCWD, &(0x7f00000003a0)='/dev/loop5\x00', 0x0, 0x0)
write(r1, &(0x7f0000000400)=@repeat(0x41, 0x10000), 0x10000)
pread64(r2, &(0x7f0000000500)=""/4096, 4096, 0)
pread64(r3, &(0x7f0000000500), 4096, 0)
pread64(r4, &(0x7f0000000500), 4096, 0)
pread64(r5, &(0x7f0000000500), 4096, 0)
pread64(r6, &(0x7f0000000500), 4096, 0)
pread64(r7, &(0x7f0000000500), 4096, 0)
close(r1)
close(r2)
close(r3)
close(r4)
close(r5)
close(r6)
close(r7)
umount2(&(0x7f0000000100)='./mnt\x00', 0x0) SyzkallerCommit:31e9c887f7dc24e04b3ca70d0d54fc34141844b0]
|
| 1/1 |
2026/03/06 00:00 |
action |
provide-var |
0m
Results: map[DescriptionFiles:[acpi_thermal_rel.txt aio.txt auto.txt binfmt.txt bpf.txt bpf_prog.txt bpf_trace.txt cgroup.txt damon.txt dev_ashmem.txt dev_bifrost.txt dev_binder.txt dev_binderfs.txt dev_block.txt dev_bsg.txt dev_bus_usb.txt dev_camx.txt dev_cdrom.txt dev_cec.txt dev_char_usb.txt dev_comedi.txt dev_dma_heap.txt dev_dri.txt dev_dsp.txt dev_dvb_demux.txt dev_dvb_dvr.txt dev_dvb_frontend.txt dev_fb.txt dev_floppy.txt dev_hidraw.txt dev_i2c.txt dev_i915.txt dev_img_rogue.txt dev_infiniband_rdma.txt dev_infiniband_rdma_cm.txt dev_input.txt dev_iommu.txt dev_kvm.txt dev_kvm_amd64.txt dev_kvm_arm64.txt dev_kvm_extra.txt dev_kvm_riscv64.txt dev_loop.txt dev_mali.txt dev_media.txt dev_msm.txt dev_msr.txt dev_nbd.txt dev_net_tun.txt dev_panthor.txt dev_ppp.txt dev_ptmx.txt dev_ptp.txt dev_qat_adf_ctl.txt dev_qrtr_tun.txt dev_random.txt dev_rfkill.txt dev_rtc.txt dev_sequencer.txt dev_sg.txt dev_snapshot.txt dev_snd_control.txt dev_snd_hw.txt dev_snd_midi.txt dev_snd_pcm.txt dev_snd_seq.txt dev_snd_timer.txt dev_sr.txt dev_sw_sync.txt dev_tlk_device.txt dev_trusty.txt dev_udmabuf.txt dev_uhid.txt dev_uinput.txt dev_usb_hiddev.txt dev_usbmon.txt dev_userio.txt dev_vfio.txt dev_vga_arbiter.txt dev_vhci.txt dev_video4linux.txt dev_video4linux_vim2m.txt dev_virtual_nci.txt dev_vtpm.txt fanotify.txt filesystem.txt fs_9p.txt fs_fuse.txt fs_incfs.txt fs_ioctl.txt fs_ioctl_autofs.txt fs_ioctl_btrfs.txt fs_ioctl_ext4.txt fs_ioctl_f2fs.txt fs_ioctl_fat.txt fs_ioctl_fscrypt.txt fs_ioctl_fsverity.txt fs_ioctl_xfs.txt futex.txt hafnium.txt inotify.txt io_uring.txt ipc.txt key.txt kfuzztest.txt l2cap.txt landlock.txt lsm.txt namespaces.txt net_80211.txt netfilter.txt netfilter_arp.txt netfilter_bridge.txt netfilter_ipv4.txt netfilter_ipv6.txt netfilter_ipvs.txt netfilter_targets.txt pagemap_ioctl.txt perf.txt prctl.txt quotactl.txt seccomp.txt security_apparmor.txt security_selinux.txt security_smack.txt socket.txt socket_alg.txt socket_ax25.txt socket_bluetooth.txt socket_caif.txt socket_can.txt socket_ieee802154.txt socket_inet.txt socket_inet6.txt socket_inet_dccp.txt socket_inet_icmp.txt socket_inet_igmp.txt socket_inet_l2tp.txt socket_inet_sctp.txt socket_inet_tcp.txt socket_inet_udp.txt socket_ip_tunnel.txt socket_isdn.txt socket_kcm.txt socket_key.txt socket_llc.txt socket_netlink.txt socket_netlink_audit.txt socket_netlink_crypto.txt socket_netlink_generic.txt socket_netlink_generic_80211.txt socket_netlink_generic_batadv.txt socket_netlink_generic_devlink.txt socket_netlink_generic_ethtool.txt socket_netlink_generic_fou.txt socket_netlink_generic_gtp.txt socket_netlink_generic_mptcp.txt socket_netlink_generic_net_dm.txt socket_netlink_generic_netlabel.txt socket_netlink_generic_nfc.txt socket_netlink_generic_seg6.txt socket_netlink_generic_smc.txt socket_netlink_generic_team.txt socket_netlink_generic_wireguard.txt socket_netlink_netfilter.txt socket_netlink_netfilter_acct.txt socket_netlink_netfilter_conntrack.txt socket_netlink_netfilter_conntrack_exp.txt socket_netlink_netfilter_conntrack_helper.txt socket_netlink_netfilter_ipset.txt socket_netlink_netfilter_log.txt socket_netlink_netfilter_nft_compat.txt socket_netlink_netfilter_nftables.txt socket_netlink_netfilter_osf.txt socket_netlink_netfilter_queue.txt socket_netlink_netfilter_timeout.txt socket_netlink_rdma.txt socket_netlink_route.txt socket_netlink_route_sched.txt socket_netlink_route_sched_retired.txt socket_netlink_sock_diag.txt socket_netlink_xfrm.txt socket_netrom.txt socket_nfc.txt socket_nvme_of_tcp.txt socket_packet.txt socket_phonet.txt socket_pppox.txt socket_qipcrtr.txt socket_rds.txt socket_rose.txt socket_rxrpc.txt socket_tipc.txt socket_tipc_netlink.txt socket_unix.txt socket_vnet.txt socket_x25.txt socket_xdp.txt sys.txt uffd.txt usbip.txt vmw_vmci.txt vnet.txt vnet_mptcp.txt vusb.txt watch_queue.txt xattr.txt] SyzkallerCommit:31e9c887f7dc24e04b3ca70d0d54fc34141844b0]
|
| 2/1 |
2026/03/06 00:00 |
action |
kernel-checkouter |
0m
Results: map[KernelSrc:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/src/0e0543b6728a481f7d36ab5dee63cf72a341470b]
|
| 3/1 |
2026/03/06 00:00 |
action |
kernel-builder |
0m
Results: map[KernelObj:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/ab46ffce72d0488f35bcd81d33f5cf480fb66a36]
|
| 4/1 |
2026/03/06 00:00 |
agent |
crash-repro-finder |
3m
Model:
Results: map[ReproOpts:{
"threaded": true,
"repeat": true,
"procs": 1
}]
Instruction:
You are an expert in linux kernel fuzzing. Your goal is to write a syzkaller program to trigger a specific bug.
Print only the syz program that could be executed directly, without backticks.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt:
Bug Title: KCSAN: data-race in _copy_to_iter / fat_mirror_bhs
Original Crash Report:
==================================================================
BUG: KCSAN: data-race in _copy_to_iter / fat_mirror_bhs
write to 0xffff888121b8d000 of 2048 bytes by task 11987 on cpu 0:
fat_mirror_bhs+0x1df/0x320 fs/fat/fatent.c:395
fat_alloc_clusters+0xb48/0xc50 fs/fat/fatent.c:543
fat_add_cluster fs/fat/inode.c:108 [inline]
__fat_get_block fs/fat/inode.c:155 [inline]
fat_get_block+0x258/0x5e0 fs/fat/inode.c:190
__block_write_begin_int+0x400/0xf90 fs/buffer.c:2142
block_write_begin fs/buffer.c:2253 [inline]
cont_write_begin+0x5fe/0x970 fs/buffer.c:2591
fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230
generic_perform_write+0x183/0x490 mm/filemap.c:4314
__generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431
generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457
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/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
read to 0xffff888121b8d000 of 512 bytes by task 22411 on cpu 1:
instrument_copy_to_user include/linux/instrumented.h:130 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
iterate_and_advance include/linux/iov_iter.h:330 [inline]
_copy_to_iter+0x130/0xea0 lib/iov_iter.c:197
copy_page_to_iter+0x18f/0x2d0 lib/iov_iter.c:374
copy_folio_to_iter include/linux/uio.h:204 [inline]
filemap_read+0x407/0xa10 mm/filemap.c:2851
blkdev_read_iter+0x22d/0x2e0 block/fops.c:855
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x6c0/0x7f0 fs/read_write.c:574
ksys_read+0xdc/0x1a0 fs/read_write.c:717
__do_sys_read fs/read_write.c:726 [inline]
__se_sys_read fs/read_write.c:724 [inline]
__x64_sys_read+0x40/0x50 fs/read_write.c:724
x64_sys_call+0x2886/0x3020 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22411 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================
The list of existing description files:
acpi_thermal_rel.txt
aio.txt
auto.txt
binfmt.txt
bpf.txt
bpf_prog.txt
bpf_trace.txt
cgroup.txt
damon.txt
dev_ashmem.txt
dev_bifrost.txt
dev_binder.txt
dev_binderfs.txt
dev_block.txt
dev_bsg.txt
dev_bus_usb.txt
dev_camx.txt
dev_cdrom.txt
dev_cec.txt
dev_char_usb.txt
dev_comedi.txt
dev_dma_heap.txt
dev_dri.txt
dev_dsp.txt
dev_dvb_demux.txt
dev_dvb_dvr.txt
dev_dvb_frontend.txt
dev_fb.txt
dev_floppy.txt
dev_hidraw.txt
dev_i2c.txt
dev_i915.txt
dev_img_rogue.txt
dev_infiniband_rdma.txt
dev_infiniband_rdma_cm.txt
dev_input.txt
dev_iommu.txt
dev_kvm.txt
dev_kvm_amd64.txt
dev_kvm_arm64.txt
dev_kvm_extra.txt
dev_kvm_riscv64.txt
dev_loop.txt
dev_mali.txt
dev_media.txt
dev_msm.txt
dev_msr.txt
dev_nbd.txt
dev_net_tun.txt
dev_panthor.txt
dev_ppp.txt
dev_ptmx.txt
dev_ptp.txt
dev_qat_adf_ctl.txt
dev_qrtr_tun.txt
dev_random.txt
dev_rfkill.txt
dev_rtc.txt
dev_sequencer.txt
dev_sg.txt
dev_snapshot.txt
dev_snd_control.txt
dev_snd_hw.txt
dev_snd_midi.txt
dev_snd_pcm.txt
dev_snd_seq.txt
dev_snd_timer.txt
dev_sr.txt
dev_sw_sync.txt
dev_tlk_device.txt
dev_trusty.txt
dev_udmabuf.txt
dev_uhid.txt
dev_uinput.txt
dev_usb_hiddev.txt
dev_usbmon.txt
dev_userio.txt
dev_vfio.txt
dev_vga_arbiter.txt
dev_vhci.txt
dev_video4linux.txt
dev_video4linux_vim2m.txt
dev_virtual_nci.txt
dev_vtpm.txt
fanotify.txt
filesystem.txt
fs_9p.txt
fs_fuse.txt
fs_incfs.txt
fs_ioctl.txt
fs_ioctl_autofs.txt
fs_ioctl_btrfs.txt
fs_ioctl_ext4.txt
fs_ioctl_f2fs.txt
fs_ioctl_fat.txt
fs_ioctl_fscrypt.txt
fs_ioctl_fsverity.txt
fs_ioctl_xfs.txt
futex.txt
hafnium.txt
inotify.txt
io_uring.txt
ipc.txt
key.txt
kfuzztest.txt
l2cap.txt
landlock.txt
lsm.txt
namespaces.txt
net_80211.txt
netfilter.txt
netfilter_arp.txt
netfilter_bridge.txt
netfilter_ipv4.txt
netfilter_ipv6.txt
netfilter_ipvs.txt
netfilter_targets.txt
pagemap_ioctl.txt
perf.txt
prctl.txt
quotactl.txt
seccomp.txt
security_apparmor.txt
security_selinux.txt
security_smack.txt
socket.txt
socket_alg.txt
socket_ax25.txt
socket_bluetooth.txt
socket_caif.txt
socket_can.txt
socket_ieee802154.txt
socket_inet.txt
socket_inet6.txt
socket_inet_dccp.txt
socket_inet_icmp.txt
socket_inet_igmp.txt
socket_inet_l2tp.txt
socket_inet_sctp.txt
socket_inet_tcp.txt
socket_inet_udp.txt
socket_ip_tunnel.txt
socket_isdn.txt
socket_kcm.txt
socket_key.txt
socket_llc.txt
socket_netlink.txt
socket_netlink_audit.txt
socket_netlink_crypto.txt
socket_netlink_generic.txt
socket_netlink_generic_80211.txt
socket_netlink_generic_batadv.txt
socket_netlink_generic_devlink.txt
socket_netlink_generic_ethtool.txt
socket_netlink_generic_fou.txt
socket_netlink_generic_gtp.txt
socket_netlink_generic_mptcp.txt
socket_netlink_generic_net_dm.txt
socket_netlink_generic_netlabel.txt
socket_netlink_generic_nfc.txt
socket_netlink_generic_seg6.txt
socket_netlink_generic_smc.txt
socket_netlink_generic_team.txt
socket_netlink_generic_wireguard.txt
socket_netlink_netfilter.txt
socket_netlink_netfilter_acct.txt
socket_netlink_netfilter_conntrack.txt
socket_netlink_netfilter_conntrack_exp.txt
socket_netlink_netfilter_conntrack_helper.txt
socket_netlink_netfilter_ipset.txt
socket_netlink_netfilter_log.txt
socket_netlink_netfilter_nft_compat.txt
socket_netlink_netfilter_nftables.txt
socket_netlink_netfilter_osf.txt
socket_netlink_netfilter_queue.txt
socket_netlink_netfilter_timeout.txt
socket_netlink_rdma.txt
socket_netlink_route.txt
socket_netlink_route_sched.txt
socket_netlink_route_sched_retired.txt
socket_netlink_sock_diag.txt
socket_netlink_xfrm.txt
socket_netrom.txt
socket_nfc.txt
socket_nvme_of_tcp.txt
socket_packet.txt
socket_phonet.txt
socket_pppox.txt
socket_qipcrtr.txt
socket_rds.txt
socket_rose.txt
socket_rxrpc.txt
socket_tipc.txt
socket_tipc_netlink.txt
socket_unix.txt
socket_vnet.txt
socket_x25.txt
socket_xdp.txt
sys.txt
uffd.txt
usbip.txt
vmw_vmci.txt
vnet.txt
vnet_mptcp.txt
vusb.txt
watch_queue.txt
xattr.txt
Reply: r0 = syz_mount_image$vfat(&(0x7f0000000000)='vfat\x00', &(0x7f0000000100)='./mnt\x00', 0x0, 0x0, 0x0, 0x0, 0x0)
r1 = openat(AT_FDCWD, &(0x7f0000000200)='./mnt/file0\x00', 0x42, 0x1ff)
r2 = openat(AT_FDCWD, &(0x7f0000000300)='/dev/loop0\x00', 0x0, 0x0)
r3 = openat(AT_FDCWD, &(0x7f0000000320)='/dev/loop1\x00', 0x0, 0x0)
r4 = openat(AT_FDCWD, &(0x7f0000000340)='/dev/loop2\x00', 0x0, 0x0)
r5 = openat(AT_FDCWD, &(0x7f0000000360)='/dev/loop3\x00', 0x0, 0x0)
r6 = openat(AT_FDCWD, &(0x7f0000000380)='/dev/loop4\x00', 0x0, 0x0)
r7 = openat(AT_FDCWD, &(0x7f00000003a0)='/dev/loop5\x00', 0x0, 0x0)
write(r1, &(0x7f0000000400)=@repeat(0x41, 0x10000), 0x10000)
pread64(r2, &(0x7f0000000500)=""/4096, 4096, 0)
pread64(r3, &(0x7f0000000500), 4096, 0)
pread64(r4, &(0x7f0000000500), 4096, 0)
pread64(r5, &(0x7f0000000500), 4096, 0)
pread64(r6, &(0x7f0000000500), 4096, 0)
pread64(r7, &(0x7f0000000500), 4096, 0)
close(r1)
close(r2)
close(r3)
close(r4)
close(r5)
close(r6)
close(r7)
umount2(&(0x7f0000000100)='./mnt\x00', 0x0)
|
| 5/2 |
2026/03/06 00:00 |
llm |
crash-repro-finder |
1m
Model:
Tokens:
input: 3209
output: 42
thoughts: 9361
Thoughts: **Reproducing a KCSAN Data-Race in the FAT Filesystem**
Okay, here's the plan. I'm aiming to reproduce a KCSAN data-race bug in the Linux kernel, specifically the one reported with the `fat_mirror_bhs` (write) and `_copy_to_iter` (read) conflict. The key is to orchestrate a scenario where one thread is modifying the FAT metadata while another is reading the raw block device.
First, I need to use syzkaller to create this environment. It looks like `syz_mount_image` will be my best friend here. I'll use it to set up a vfat filesystem on a loop device. This will handle creating a backing file, formatting it, and mounting it, which is convenient. I’ll make sure to create and mount a filesystem image via `syz_mount_image`, targeting a FAT filesystem. Then, I need to open a file *within* that mounted filesystem for writing. I will open the loop device itself, as it is the block device, for reading.
The write operation is crucial. I need to write enough data to trigger cluster allocation and, therefore, the `fat_mirror_bhs` function. This function is the one that updates the FAT tables (it also mirrors the tables), which is what triggers the write side of the race.
The read operation will be simpler. By reading the loop device directly, I should be able to trigger `blkdev_read_iter`. The crash report suggests that this is where the `_copy_to_iter` and eventual data race happens.
Now, to make it work, I need to do the following:
1. Use `syz_mount_image` to set up the FAT filesystem (vfat).
2. Open a file within the mount (e.g. `mnt/file`).
3. Open the loop device itself (e.g., `/dev/loop0`). Since I don't know the exact loop device name, I will simply open `loop0`.
4. Trigger the race by running two separate operations in two separate threads:
* Thread 1: Write a sizable amount of data to the file within the filesystem, thus triggering `fat_alloc_clusters` and subsequently `fat_mirror_bhs`. I will run the `write` call in a loop, possibly with larger data chunks to increase the chance of allocation.
* Thread 2: Read from the loop device.
The `syz_mount_image` call itself should be relatively straightforward. I will use the standard arguments, specifying "vfat" as the filesystem type and a mount point directory. I'll set a few `0`'s for flags. `syz_mount_image` needs to generate a valid FAT image.
I'll then open the created file (`mnt/file`) to write data to it. The block device is accessed using `syz_open_dev("loop", 0, 0)`, to grab the underlying `/dev/loop0`. I'll try just the first loop device, as `syz_mount_image` will usually grab it. I will `write` to the file with a data of size `0x10000`, and `read` (specifically, `pread`) from `/dev/loop0` with the same size. To maximize the chance of triggering the race, I'll use `threaded=true` and `repeat=true` in the `ReproOpts`.
The key is that `blkdev_read_iter` is reading the buffer head data (page cache) on the block device. At the same time, `fat_mirror_bhs` updates those very same pages in memory. It is a classic data race.
|
| 6/2 |
2026/03/06 00:01 |
tool |
set-results |
0m
Args: map[ReproOpts:{
"threaded": true,
"repeat": true,
"procs": 1
}]
Results: map[ReproOpts:{
"threaded": true,
"repeat": true,
"procs": 1
}]
|
| 7/2 |
2026/03/06 00:01 |
llm |
crash-repro-finder |
1m
Model:
Tokens:
input: 4103
output: 756
thoughts: 12919
Thoughts: **Reproducing the KCSAN Data-Race in `fat_mirror_bhs`**
Okay, so I need to craft a syzkaller program to trigger this nasty data race between `fat_mirror_bhs` and `_copy_to_iter`. The goal is a reliable reproduction. The crash report shows a race where a write from a function that mirrors FAT entries (`fat_mirror_bhs`, called during file allocation) collides with a read (via `_copy_to_iter`) from the underlying block device. This happens on a FAT filesystem.
Here's my plan:
1. **Set up:** First, I'll use `syz_mount_image` to create a loopback device and mount a vfat filesystem. This is crucial because `fat_mirror_bhs` is specific to FAT filesystems. `syz_mount_image` handles the image creation and mounting process. I'm going to specify vfat. The mount point will be `./mnt`. I don't directly get the loop device name back but a standard syzkaller setup will use `/dev/loop0` as the first available, so I'll try that, and the first few loop devices.
2. **Concurrency:** Next, I'll launch two threads (or utilize the `threaded: true` syzkaller directive). The first thread will open a file within the mounted vfat filesystem. Then, the first thread writes to a file in the mount. I will open the loop device to mirror the crash. To trigger cluster allocation in `fat_mirror_bhs`, I will write to it. I want to allocate space to force `fat_alloc_clusters` calls which will lead to writes to the FAT. Concurrently, the other thread will open the underlying block device (loop device) and read from it using `pread64` from the start of the device. This is where I'll read from. I'm opening a few loop devices to ensure I'm hitting the right one or at least overlapping.
3. **Race Condition Exposure:** This interleaved read and write is the core. The write operation extends the file, which forces FAT metadata updates and likely `fat_mirror_bhs` to perform its mirroring. The read operation directly accesses the block device, potentially reading the data concurrently while `fat_mirror_bhs` is modifying it. The `repeat: true` is set, and it's set to run this loop many times, increasing the chance of hitting the race.
4. **Cleanup:** After the loop, the file and loop devices will be closed. I am not using `close` but the cleanup will be done on exit. Finally, `umount2` will be called to unmount the vfat filesystem, cleaning up the loop device and mount point. This is to avoid resource exhaustion and potential mount conflicts in subsequent test iterations.
I'm confident this should trigger the race. Here is the syzkaller program I've crafted for this.
```
r0 = syz_mount_image$vfat(&(0x7f0000000000)='vfat\x00', &(0x7f0000000100)='./mnt\x00', 0x0, 0x0, 0x0, 0x0, 0x0)
r1 = openat(AT_FDCWD, &(0x7f0000000200)='./mnt/file0\x00', 0x42, 0x1ff)
r2 = openat(AT_FDCWD, &(0x7f0000000300)='/dev/loop0\x00', 0x0, 0x0)
r3 = openat(AT_FDCWD, &(0x7f0000000320)='/dev/loop1\x00', 0x0, 0x0)
r4 = openat(AT_FDCWD, &(0x7f0000000340)='/dev/loop2\x00', 0x0, 0x0)
r5 = openat(AT_FDCWD, &(0x7f0000000360)='/dev/loop3\x00', 0x0, 0x0)
r6 = openat(AT_FDCWD, &(0x7f0000000380)='/dev/loop4\x00', 0x0, 0x0)
r7
|