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

write to 0xffffffff8686c850 of 8 bytes by task 121 on cpu 0:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 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
 bio_check_eod block/blk-core.c:563 [inline]
 submit_bio_noacct+0x830/0x920 block/blk-core.c:796
 submit_bio+0x2a6/0x2c0 block/blk-core.c:916
 mpage_bio_submit_write fs/mpage.c:83 [inline]
 mpage_write_folio fs/mpage.c:588 [inline]
 mpage_writepages+0x754/0x1250 fs/mpage.c:664
 fat_writepages+0x24/0x30 fs/fat/inode.c:199
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2634
 __writeback_single_inode+0x80/0x7c0 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x48f/0xa30 fs/fs-writeback.c:1976
 wb_writeback+0x252/0x5c0 fs/fs-writeback.c:2156
 wb_do_writeback fs/fs-writeback.c:2303 [inline]
 wb_workfn+0x194/0x910 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff8686c850 of 8 bytes by task 9541 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+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 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:1379 [inline]
 nft_obj_init+0x93/0x220 net/netfilter/nf_tables_api.c:8126
 nf_tables_newobj+0x72f/0xcc0 net/netfilter/nf_tables_api.c:8321
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:524 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:647 [inline]
 nfnetlink_rcv+0xb96/0x1690 net/netfilter/nfnetlink.c:665
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5bd/0x690 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg+0x142/0x180 net/socket.c:729
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2614
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668
 __sys_sendmsg net/socket.c:2700 [inline]
 __do_sys_sendmsg net/socket.c:2705 [inline]
 __se_sys_sendmsg net/socket.c:2703 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2703
 x64_sys_call+0x191e/0x2ff0 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: 0xfffffffffffcd8f0 -> 0x00000000000631a0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9541 Comm: syz.1.1988 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================
netlink: 4 bytes leftover after parsing attributes in process `syz.1.1988'.