==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff8686b298 of 8 bytes by task 20671 on cpu 0:
 data_alloc+0x290/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x86a/0xb80 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 dev_vprintk_emit+0x24a/0x2a0 drivers/base/core.c:4891
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4902
 __netdev_printk+0x352/0x3e0 net/core/dev.c:12392
 netdev_info+0x9e/0xd0 net/core/dev.c:12447
 nsim_udp_tunnel_unset_port+0x1c8/0x1f0 drivers/net/netdevsim/udp_tunnels.c:64
 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:-1 [inline]
 udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:246 [inline]
 __udp_tunnel_nic_device_sync+0x594/0xa00 net/ipv4/udp_tunnel_nic.c:289
 udp_tunnel_nic_flush+0x234/0x320 net/ipv4/udp_tunnel_nic.c:670
 udp_tunnel_nic_unregister net/ipv4/udp_tunnel_nic.c:864 [inline]
 udp_tunnel_nic_netdevice_event+0x7ba/0xc80 net/ipv4/udp_tunnel_nic.c:904
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:453
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2180
 call_netdevice_notifiers_extack net/core/dev.c:2218 [inline]
 call_netdevice_notifiers net/core/dev.c:2232 [inline]
 unregister_netdevice_many_notify+0xd12/0x1600 net/core/dev.c:11973
 unregister_netdevice_many net/core/dev.c:12037 [inline]
 unregister_netdevice_queue+0x1fd/0x230 net/core/dev.c:11889
 unregister_netdevice include/linux/netdevice.h:3374 [inline]
 nsim_destroy+0xbd/0x340 drivers/net/netdevsim/netdev.c:1051
 __nsim_dev_port_del+0xcd/0x100 drivers/net/netdevsim/dev.c:1428
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1440 [inline]
 nsim_dev_reload_destroy+0x1a6/0x2d0 drivers/net/netdevsim/dev.c:1661
 nsim_dev_reload_down+0x77/0xa0 drivers/net/netdevsim/dev.c:968
 devlink_reload+0xad/0x5b0 net/devlink/dev.c:461
 devlink_nl_reload_doit+0x7b7/0x930 net/devlink/dev.c:584
 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0x69b/0x6f0 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x12f/0x230 net/netlink/af_netlink.c:2534
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x605/0x6c0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x609/0x720 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:727
 ____sys_sendmsg+0x350/0x4e0 net/socket.c:2566
 ___sys_sendmsg net/socket.c:2620 [inline]
 __sys_sendmsg+0x1a0/0x240 net/socket.c:2652
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0x46/0x50 net/socket.c:2655
 x64_sys_call+0x26f3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8686b298 of 8 bytes by task 20684 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x239/0xb80 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 set_capacity_and_notify+0x155/0x200 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:210
 loop_configure+0x89c/0xa30 drivers/block/loop.c:1120
 lo_ioctl+0x5fa/0x1570 drivers/block/loop.c:-1
 blkdev_ioctl+0x35b/0x450 block/ioctl.c:698
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x168d/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000007e190 -> 0x00000000001418f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 20684 Comm: syz.8.11392 Not tainted 6.14.0-syzkaller-07486-g15cb9a2b66fc #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
loop8: detected capacity change from 0 to 512
EXT4-fs warning (device loop8): ext4_enable_quotas:7170: Failed to enable quota tracking (type=0, err=-117, ino=3). Please run e2fsck to fix.
EXT4-fs (loop8): mount failed