netlink: annotate accesses to nlk->cb_running

In the Linux kernel, the following vulnerability has been resolved:

netlink: annotate accesses to nlk->cb_running

Both netlink_recvmsg() and netlink_native_seq_show() read

nlk->cb_running locklessly. Use READ_ONCE() there.

Add corresponding WRITE_ONCE() to netlink_dump() and

__netlink_dump_start()

syzbot reported:

BUG: KCSAN: data-race in __netlink_dump_start / netlink_recvmsg

write to 0xffff88813ea4db59 of 1 bytes by task 28219 on cpu 0:

__netlink_dump_start+0x3af/0x4d0 net/netlink/af_netlink.c:2399

netlink_dump_start include/linux/netlink.h:308 [inline]

rtnetlink_rcv_msg+0x70f/0x8c0 net/core/rtnetlink.c:6130

netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2577

rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6192

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:1942

sock_sendmsg_nosec net/socket.c:724 [inline]

sock_sendmsg net/socket.c:747 [inline]

sock_write_iter+0x1aa/0x230 net/socket.c:1138

call_write_iter include/linux/fs.h:1851 [inline]

new_sync_write fs/read_write.c:491 [inline]

vfs_write+0x463/0x760 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 0xffff88813ea4db59 of 1 bytes by task 28222 on cpu 1:

netlink_recvmsg+0x3b4/0x730 net/netlink/af_netlink.c:2022

sock_recvmsg_nosec+0x4c/0x80 net/socket.c:1017

____sys_recvmsg+0x2db/0x310 net/socket.c:2718

___sys_recvmsg net/socket.c:2762 [inline]

do_recvmmsg+0x2e5/0x710 net/socket.c:2856

__sys_recvmmsg net/socket.c:2935 [inline]

__do_sys_recvmmsg net/socket.c:2958 [inline]

__se_sys_recvmmsg net/socket.c:2951 [inline]

__x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951

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: 0x00 -> 0x01