KCSAN: data-race in __netlink_dump_start / netlink_setsockopt

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b6505459 Linux 5.10-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f99795500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=49375203b7a186c80f85
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [0x7f4...@gmail.com and...@kernel.org a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net da...@davemloft.net john.fa...@gmail.com ka...@fb.com kps...@chromium.org ku...@kernel.org linux-...@vger.kernel.org mkub...@suse.cz net...@vger.kernel.org songliu...@fb.com y...@fb.com]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+493752...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __netlink_dump_start / netlink_setsockopt

write to 0xffff888023f8eb04 of 4 bytes by task 17379 on cpu 0:
netlink_setsockopt+0x6ec/0x800 net/netlink/af_netlink.c:1694
__sys_setsockopt+0x2dc/0x450 net/socket.c:2132
__do_sys_setsockopt net/socket.c:2143 [inline]
__se_sys_setsockopt net/socket.c:2140 [inline]
__x64_sys_setsockopt+0x62/0x70 net/socket.c:2140
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888023f8eb04 of 4 bytes by task 17381 on cpu 1:
__netlink_dump_start+0x2a5/0x4d0 net/netlink/af_netlink.c:2360
netlink_dump_start include/linux/netlink.h:256 [inline]
rtnetlink_rcv_msg+0x6cb/0x7c0 net/core/rtnetlink.c:5525
netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2494
rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5580
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x5df/0x6b0 net/netlink/af_netlink.c:1330
netlink_sendmsg+0x6f8/0x7c0 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
sock_write_iter+0x1a4/0x200 net/socket.c:998
call_write_iter include/linux/fs.h:1903 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0x6d4/0x7c0 fs/read_write.c:605
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17381 Comm: syz-executor.3 Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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