IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
==================================================================
BUG: KCSAN: data-race in data_push_tail / string

write to 0xffffffff86e736db of 1 bytes by task 30293 on cpu 0:
 string_nocheck lib/vsprintf.c:647 [inline]
 string+0x17b/0x220 lib/vsprintf.c:725
 vsnprintf+0xb57/0xe80 lib/vsprintf.c:2782
 vscnprintf+0x3e/0x80 lib/vsprintf.c:2888
 printk_sprint kernel/printk/printk.c:2092 [inline]
 vprintk_store+0x5f2/0xb50 kernel/printk/printk.c:2206
 vprintk_emit+0xcc/0x430 kernel/printk/printk.c:2252
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2282
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2292
 __ext4_msg+0x174/0x180 fs/ext4/super.c:944
 ext4_fill_super+0x2391/0x4f00 fs/ext4/super.c:5507
 get_tree_bdev+0x2b4/0x3b0 fs/super.c:1292
 ext4_get_tree+0x18/0x20 fs/ext4/super.c:5537
 vfs_get_tree+0x49/0x190 fs/super.c:1497
 do_new_mount+0x200/0x650 fs/namespace.c:3040
 path_mount+0x4b1/0xb60 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x281/0x2d0 fs/namespace.c:3568
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff86e736d8 of 8 bytes by task 30302 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:590 [inline]
 data_push_tail+0x10f/0x440 kernel/printk/printk_ringbuffer.c:675
 data_alloc+0xbc/0x2b0 kernel/printk/printk_ringbuffer.c:1046
 prb_reserve+0x897/0xbd0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x51c/0xb50 kernel/printk/printk.c:2196
 vprintk_emit+0xcc/0x430 kernel/printk/printk.c:2252
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2282
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2292
 fib6_add+0x3f1/0x1f50 net/ipv6/ip6_fib.c:1391
 __ip6_ins_rt net/ipv6/route.c:1302 [inline]
 ip6_route_add+0x6d/0x100 net/ipv6/route.c:3847
 inet6_rtm_newroute+0x152/0x1160 net/ipv6/route.c:5512
 rtnetlink_rcv_msg+0x811/0x8c0 net/core/rtnetlink.c:6089
 netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2501
 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:6107
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x58a/0x660 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x661/0x750 net/netlink/af_netlink.c:1921
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg net/socket.c:734 [inline]
 ____sys_sendmsg+0x38f/0x500 net/socket.c:2488
 ___sys_sendmsg net/socket.c:2542 [inline]
 __sys_sendmsg+0x1f9/0x400 net/socket.c:2571
 __do_sys_sendmsg net/socket.c:2580 [inline]
 __se_sys_sendmsg net/socket.c:2578 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2578
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000100006e63 -> 0x3a2933706f6f6c28

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30302 Comm: syz-executor.1 Not tainted 5.19.0-rc8-syzkaller-00102-g33ea1340bafe-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
==================================================================
syz-executor.1 (30302) used greatest stack depth: 9664 bytes left