netlink: 4 bytes leftover after parsing attributes in process `syz-executor.5'.
==================================================================
BUG: KCSAN: data-race in data_alloc / data_push_tail

write to 0xffffffff86f0a218 of 8 bytes by task 23298 on cpu 0:
 data_alloc+0x216/0x2c0 kernel/printk/printk_ringbuffer.c:1074
 prb_reserve+0x893/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x53e/0x800 kernel/printk/printk.c:2232
 vprintk_emit+0xd0/0x430 kernel/printk/printk.c:2288
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x83/0x90 kernel/printk/printk_safe.c:50
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 printk_stack_address arch/x86/kernel/dumpstack.c:72 [inline]
 show_trace_log_lvl+0x37e/0x400 arch/x86/kernel/dumpstack.c:285
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xda/0x130 lib/dump_stack.c:106
 dump_stack+0x15/0x20 lib/dump_stack.c:113
 fail_dump lib/fault-inject.c:52 [inline]
 should_fail_ex+0x21f/0x230 lib/fault-inject.c:153
 prepare_alloc_pages mm/page_alloc.c:4541 [inline]
 __alloc_pages+0x108/0x340 mm/page_alloc.c:4757
 vma_alloc_folio+0x6a3/0x8c0 mm/mempolicy.c:2240
 shmem_alloc_folio mm/shmem.c:1579 [inline]
 shmem_alloc_and_acct_folio mm/shmem.c:1603 [inline]
 shmem_get_folio_gfp+0x801/0x1200 mm/shmem.c:1948
 shmem_get_folio mm/shmem.c:2079 [inline]
 shmem_write_begin+0xa6/0x1d0 mm/shmem.c:2573
 generic_perform_write+0x1c3/0x3d0 mm/filemap.c:3929
 __generic_file_write_iter+0xe6/0x290 mm/filemap.c:4057
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4089
 call_write_iter include/linux/fs.h:1868 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x47b/0x780 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff86f0a218 of 8 bytes by task 23299 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:590 [inline]
 data_push_tail+0x102/0x430 kernel/printk/printk_ringbuffer.c:675
 data_alloc+0xbe/0x2c0 kernel/printk/printk_ringbuffer.c:1046
 prb_reserve+0x893/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x53e/0x800 kernel/printk/printk.c:2232
 vprintk_emit+0xd0/0x430 kernel/printk/printk.c:2288
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x83/0x90 kernel/printk/printk_safe.c:50
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 __nla_validate_parse+0x15ba/0x1b50 lib/nlattr.c:615
 __nla_parse+0x40/0x50 lib/nlattr.c:700
 __nlmsg_parse include/net/netlink.h:749 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:790 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3530 [inline]
 rtnl_newlink+0x1c0/0x15a0 net/core/rtnetlink.c:3695
 rtnetlink_rcv_msg+0x807/0x8c0 net/core/rtnetlink.c:6417
 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2546
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6435
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1913
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg net/socket.c:747 [inline]
 __sys_sendto+0x246/0x300 net/socket.c:2144
 __do_sys_sendto net/socket.c:2156 [inline]
 __se_sys_sendto net/socket.c:2152 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2152
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000001000019c4 -> 0x0000000100002a21

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23299 Comm: syz-executor.5 Not tainted 6.4.0-rc6-syzkaller-00037-gb6dad5178cea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
==================================================================
syz-executor.5 (23299) used greatest stack depth: 9360 bytes left