[moderation] [kernel?] KCSAN: data-race in data_push_tail / symbol_string (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cd802e7e5f1e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=126122f4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6154604431d9aaf9
dashboard link: https://syzkaller.appspot.com/bug?extid=7b6ee5c43a6b8cc3988c
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [b...@alien8.de dave....@linux.intel.com h...@zytor.com jpoi...@kernel.org linux-...@vger.kernel.org mi...@redhat.com pet...@infradead.org tg...@linutronix.de x...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fdb14cb5e78f/disk-cd802e7e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c8b91b8b365f/vmlinux-cd802e7e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/69520a7040dd/bzImage-cd802e7e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7b6ee5...@syzkaller.appspotmail.com

BUG: KCSAN: data-race in data_push_tail / symbol_string

write to 0xffffffff88e348e0 of 1 bytes by task 18161 on cpu 0:
string_nocheck lib/vsprintf.c:643 [inline]
symbol_string+0x1ce/0x250 lib/vsprintf.c:999
pointer+0x60c/0xcf0 lib/vsprintf.c:2441
vsnprintf+0x491/0x890 lib/vsprintf.c:2856
vscnprintf+0x41/0x90 lib/vsprintf.c:2917
printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2216
vprintk_store+0x599/0x860 kernel/printk/printk.c:2336
vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
_printk+0x79/0xa0 kernel/printk/printk.c:2475
printk_stack_address arch/x86/kernel/dumpstack.c:72 [inline]
show_trace_log_lvl+0x4e3/0x560 arch/x86/kernel/dumpstack.c:284
__dump_stack+0x1d/0x30 lib/dump_stack.c:94
dump_stack_lvl+0xe8/0x140 lib/dump_stack.c:120
dump_stack+0x15/0x1b lib/dump_stack.c:129
fail_dump lib/fault-inject.c:73 [inline]
should_fail_ex+0x265/0x280 lib/fault-inject.c:174
should_fail+0xb/0x20 lib/fault-inject.c:184
should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37
strncpy_from_user+0x25/0x230 lib/strncpy_from_user.c:118
getname_flags+0xae/0x3b0 fs/namei.c:157
getname include/linux/fs.h:2852 [inline]
__do_sys_mknod fs/namei.c:4311 [inline]
__se_sys_mknod fs/namei.c:4309 [inline]
__x64_sys_mknod+0x40/0x60 fs/namei.c:4309
x64_sys_call+0x181c/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:134
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e348e0 of 8 bytes by task 17738 on cpu 1:
data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline]
data_push_tail+0xfd/0x420 kernel/printk/printk_ringbuffer.c:679
data_alloc+0xbf/0x2b0 kernel/printk/printk_ringbuffer.c:1054
prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4917
dev_printk_emit+0x84/0xb0 drivers/base/core.c:4928
__netdev_printk+0x35c/0x3e0 net/core/dev.c:12393
netdev_info+0x9b/0xd0 net/core/dev.c:12448
nsim_udp_tunnel_set_port+0x171/0x190 drivers/net/netdevsim/udp_tunnels.c:34
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+0x564/0x9c0 net/ipv4/udp_tunnel_nic.c:289
udp_tunnel_nic_device_sync net/ipv4/udp_tunnel_nic.c:312 [inline]
__udp_tunnel_nic_add_port+0x6a9/0x720 net/ipv4/udp_tunnel_nic.c:531
udp_tunnel_nic_add_port include/net/udp_tunnel.h:350 [inline]
udp_tunnel_push_rx_port+0xe9/0x120 net/ipv4/udp_tunnel_core.c:96
geneve_offload_rx_ports drivers/net/geneve.c:1185 [inline]
geneve_netdevice_event+0x173/0x1b0 drivers/net/geneve.c:1929
notifier_call_chain kernel/notifier.c:85 [inline]
raw_notifier_call_chain+0x6c/0x1b0 kernel/notifier.c:453
call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2176
call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
call_netdevice_notifiers+0x48/0x70 net/core/dev.c:2228
udp_tunnel_get_rx_info include/net/udp_tunnel.h:138 [inline]
udp_tunnel_nic_register net/ipv4/udp_tunnel_nic.c:825 [inline]
udp_tunnel_nic_netdevice_event+0xa54/0xc90 net/ipv4/udp_tunnel_nic.c:893
notifier_call_chain kernel/notifier.c:85 [inline]
raw_notifier_call_chain+0x6c/0x1b0 kernel/notifier.c:453
call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2176
call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
call_netdevice_notifiers net/core/dev.c:2228 [inline]
register_netdevice+0xd48/0xf10 net/core/dev.c:11035
nsim_init_netdevsim drivers/net/netdevsim/netdev.c:960 [inline]
nsim_create+0x5b7/0x780 drivers/net/netdevsim/netdev.c:1028
__nsim_dev_port_add+0x477/0x640 drivers/net/netdevsim/dev.c:1393
nsim_dev_port_add_all+0x31/0xc0 drivers/net/netdevsim/dev.c:1449
nsim_dev_reload_create drivers/net/netdevsim/dev.c:1501 [inline]
nsim_dev_reload_up+0x30c/0x480 drivers/net/netdevsim/dev.c:988
devlink_reload+0x318/0x580 net/devlink/dev.c:474
devlink_nl_reload_doit+0x772/0x8f0 net/devlink/dev.c:584
genl_family_rcv_msg_doit+0x140/0x1b0 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x422/0x460 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x120/0x220 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+0x59e/0x670 net/netlink/af_netlink.c:1339
netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1883
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x142/0x180 net/socket.c:727
____sys_sendmsg+0x31e/0x4e0 net/socket.c:2566
___sys_sendmsg+0x17b/0x1d0 net/socket.c:2620
__sys_sendmsg net/socket.c:2652 [inline]
__do_sys_sendmsg net/socket.c:2657 [inline]
__se_sys_sendmsg net/socket.c:2655 [inline]
__x64_sys_sendmsg+0xd4/0x160 net/socket.c:2655
x64_sys_call+0x2999/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000fffff5bb -> 0x00000000ff000a30

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17738 Comm: syz.5.2763 Not tainted 6.15.0-rc5-syzkaller-00353-gcd802e7e5f1e #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================


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[syzbot]

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