[moderation] [kernel?] KCSAN: data-race in data_push_tail / hex_string (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6832a9317eee Merge tag 'net-6.16-rc7' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12875382580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8b73fe883c5b6ae
dashboard link: https://syzkaller.appspot.com/bug?extid=bc481c0f87c5cf781cf4
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/1bb7740ffc5f/disk-6832a931.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2dc443e95dff/vmlinux-6832a931.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bdf2866bfebf/bzImage-6832a931.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bc481c...@syzkaller.appspotmail.com

BUG: KCSAN: data-race in data_push_tail / hex_string

write to 0xffffffff88e446b0 of 1 bytes by task 8056 on cpu 0:
hex_string+0x28e/0x330 lib/vsprintf.c:1209
pointer+0x2d7/0xcf0 lib/vsprintf.c:2468
vsnprintf+0x491/0x890 lib/vsprintf.c:2878
vscnprintf+0x41/0x90 lib/vsprintf.c:2939
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
show_opcodes+0xfe/0x120 arch/x86/kernel/dumpstack.c:121
show_iret_regs+0x12/0x40 arch/x86/kernel/dumpstack.c:147
__show_regs+0x2a/0x440 arch/x86/kernel/process_64.c:77
show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline]
show_trace_log_lvl+0x423/0x560 arch/x86/kernel/dumpstack.c:298
__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_alloc_page+0xf2/0x100 mm/fail_page_alloc.c:44
prepare_alloc_pages mm/page_alloc.c:4734 [inline]
__alloc_frozen_pages_noprof+0xff/0x360 mm/page_alloc.c:4948
alloc_pages_mpol+0xb3/0x250 mm/mempolicy.c:2419
folio_alloc_mpol_noprof mm/mempolicy.c:2438 [inline]
vma_alloc_folio_noprof+0x1aa/0x300 mm/mempolicy.c:2473
folio_prealloc mm/memory.c:-1 [inline]
alloc_anon_folio mm/memory.c:5014 [inline]
do_anonymous_page mm/memory.c:5071 [inline]
do_pte_missing mm/memory.c:4249 [inline]
handle_pte_fault mm/memory.c:6069 [inline]
__handle_mm_fault mm/memory.c:6212 [inline]
handle_mm_fault+0xec2/0x2be0 mm/memory.c:6381
do_user_addr_fault+0x3fe/0x1090 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
__put_user_8+0xd/0x20 arch/x86/lib/putuser.S:113
processcompl+0x3eb/0x410 drivers/usb/core/devio.c:2073
proc_reapurb drivers/usb/core/devio.c:2112 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2617 [inline]
usbdev_ioctl+0x1ea/0x1710 drivers/usb/core/devio.c:2827
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xce/0x140 fs/ioctl.c:893
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e446b0 of 8 bytes by task 8058 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
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
__nla_validate_parse+0x1738/0x1d00 lib/nlattr.c:647
__nla_parse+0x40/0x60 lib/nlattr.c:732
nla_parse_nested_deprecated include/net/netlink.h:1365 [inline]
rtnl_newlink+0x793/0x12d0 net/core/rtnetlink.c:4002
rtnetlink_rcv_msg+0x5fe/0x6d0 net/core/rtnetlink.c:6944
netlink_rcv_skb+0x120/0x220 net/netlink/af_netlink.c:2552
rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6971
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x5a8/0x680 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x145/0x180 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+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000100002fca -> 0x2031302066302039

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8058 Comm: syz.3.13652 Not tainted 6.16.0-rc6-syzkaller-00121-g6832a9317eee #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

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