syzbot

map[ReproOpts:threaded=true, collide=true, repeat=true, procs=8 ReproSyz:io_setup(0xa, &(0x7f0000000000)=<r0=>0x0)
r1 = openat(0xffffffffffffff9c, &(0x7f0000000040)='file\x00', 0x42, 0x1ff)
write(r1, &(0x7f0000000200)='data', 0x4)
io_submit(r0, 0x1, &(0x7f0000000080)=@arr=[&(0x7f00000000c0)={0x0, 0x0, 0x0, 0x0, 0x0, r1, &(0x7f0000000100), 0x4, 0x0, 0x0, 0x0, 0x0}])
io_getevents(r0, 0x0, 0xa, &(0x7f0000000140), 0x0)
io_destroy(r0) SyzkallerCommit:31e9c887f7dc24e04b3ca70d0d54fc34141844b0]

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]

map[KernelSrc:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/src/2fdd1b0b70843cf11339656b168b6d2ccec9cbc2]

map[KernelObj:/usr/local/google/home/dvyukov/syzkaller/agent/workdir/cache/build/b07903d644582d0e293db32421ead036a9fd68a4]

gemini-3-pro-preview

map[ReproOpts:threaded=true, collide=true, repeat=true, procs=8]

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.

Bug Title: KCSAN: data-race in aio_read_events / iocb_put

Original Crash Report:
==================================================================
BUG: KCSAN: data-race in aio_read_events / iocb_put

write to 0xffff88813ae2800c of 4 bytes by task 10185 on cpu 1:
 aio_complete fs/aio.c:1162 [inline]
 iocb_put+0x18c/0x680 fs/aio.c:1209
 io_submit_one+0xbcb/0x1350 fs/aio.c:2056
 __do_sys_io_submit fs/aio.c:2112 [inline]
 __se_sys_io_submit+0xfb/0x280 fs/aio.c:2082
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2082
 x64_sys_call+0x19d5/0x3020 arch/x86/include/generated/asm/syscalls_64.h:210
 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 0xffff88813ae2800c of 4 bytes by task 10186 on cpu 0:
 aio_read_events_ring fs/aio.c:1238 [inline]
 aio_read_events+0xb2/0x400 fs/aio.c:1298
 read_events fs/aio.c:1334 [inline]
 do_io_getevents+0x11b/0x450 fs/aio.c:2230
 __do_sys_io_getevents fs/aio.c:2263 [inline]
 __se_sys_io_getevents fs/aio.c:2251 [inline]
 __x64_sys_io_getevents+0xca/0x190 fs/aio.c:2251
 x64_sys_call+0x2cfe/0x3020 arch/x86/include/generated/asm/syscalls_64.h:209
 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

value changed: 0x00000003 -> 0x00000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10186 Comm: syz.7.1697 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================


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

io_setup(0xa, &(0x7f0000000000)=<r0=>0x0)
r1 = openat(0xffffffffffffff9c, &(0x7f0000000040)='file\x00', 0x42, 0x1ff)
write(r1, &(0x7f0000000200)='data', 0x4)
io_submit(r0, 0x1, &(0x7f0000000080)=@arr=[&(0x7f00000000c0)={0x0, 0x0, 0x0, 0x0, 0x0, r1, &(0x7f0000000100), 0x4, 0x0, 0x0, 0x0, 0x0}])
io_getevents(r0, 0x0, 0xa, &(0x7f0000000140), 0x0)
io_destroy(r0)

gemini-3-pro-preview

							input: 2702
							output: 33
							thoughts: 17620
						

**Reproducing a KCSAN Data Race in AIO with syzkaller**

Alright, let's break down how we're going to use a syzkaller program to trigger that pesky data race in `aio_read_events` and `iocb_put`. The crash report points to a race on an address within the ring buffer's metadata, specifically the `tail` pointer, where the value is changing between a write (by `io_submit` completing) and a read (by `io_getevents`).

The plan is to leverage AIO's concurrent nature. We need two threads hammering the same AIO context: one submitting read requests using `io_submit`, and another diligently reading events with `io_getevents`. The core of the issue is around the `ring->tail` update in `aio_complete` and the concurrent access in `aio_read_events_ring`. If we can get them to step on each other's toes with our IO requests, we have a good chance of triggering the KCSAN data race. The key is in `iocb_put` when `refcount` of `iocb` is zero, we want it to call `aio_complete`, but it is also accessed by `io_getevents` at the same time.

To set this up, we'll start with `io_setup` to create an AIO context. Then, we need a file descriptor. I can open a file or just use `openat`. We'll write some data to this file so we can trigger a read that will *synchronously* complete. Since the AIO request will complete synchronously, `io_submit` will trigger `aio_complete` immediately. This triggers the write to ring buffer's tail pointer. Meanwhile, we'll set up a loop that calls `io_getevents`. This loop will try to read the events. If `io_getevents` is reading while `aio_complete` writes to the ring, then we will have a race.

The strategy here is to get `io_submit` and `io_getevents` to collide. We will make our read calls synchronous, so `aio_complete` is called from within the `io_submit_one` and our read calls will also try to access the ring. By running these syscalls in threads, we should trigger the issue. I have constructed an `iocb` struct to read from a file, but I have set the read size to small (4 bytes), so the call completes quickly.

The program will look like this:

```syzkaller
io_setup(0xa, &(0x7f0000000000)=<r0=>0x0)
r1 = openat(0xffffffffffffff9c, &(0x7f0000000040)='file\x00', 0x42, 0x1ff)
write(r1, &(0x7f0000000200)='data', 0x4)
io_submit(r0, 0x1, &(0x7f0000000080)=@arr=[&(0x7f00000000c0)={0x0, 0x0, 0x0, 0x0, 0x0, r1, &(0x7f0000000100), 0x4, 0x0, 0x0, 0x0, 0x0}])
io_getevents(r0, 0x0, 0xa, &(0x7f0000000140), 0x0)
io_destroy(r0)
```

We'll set `ReproOpts` to `threaded=true`, `collide=true`, `repeat=true` and `procs=8`. The number of processes gives us multiple threads (since `collide=true` and `threaded=true`). This will have `io_submit` running frequently, and `io_getevents` checking the ring frequently. The goal is to trigger the write/read race.

map[ReproOpts:threaded=true, collide=true, repeat=true, procs=8]

map[ReproOpts:threaded=true, collide=true, repeat=true, procs=8]

gemini-3-pro-preview

							input: 21301
							output: 275
							thoughts: 0