KCSAN: data-race in ep_poll / ep_poll_callback

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b4bd9343 x86, kcsan: Enable KCSAN for x86
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1557f1db600000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0906aa620713d80
dashboard link: https://syzkaller.appspot.com/bug?extid=4e154dd1f4745e2bfadd
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk el...@google.com]

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4e154d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ep_poll / ep_poll_callback

write to 0xffff8881232b8650 of 8 bytes by interrupt on cpu 0:
list_add_tail_lockless fs/eventpoll.c:1163 [inline]
ep_poll_callback+0x5e7/0x6a0 fs/eventpoll.c:1253
__wake_up_common+0x7b/0x180 kernel/sched/wait.c:93
__wake_up_common_lock+0x77/0xb0 kernel/sched/wait.c:123
__wake_up_sync_key+0x19/0x20 kernel/sched/wait.c:196
sock_def_readable+0xa9/0x140 net/core/sock.c:2786
tcp_data_ready+0x7d/0xd0 net/ipv4/tcp_input.c:4706
tcp_rcv_established+0xd0c/0xf50 net/ipv4/tcp_input.c:5632
tcp_v4_do_rcv+0x381/0x4e0 net/ipv4/tcp_ipv4.c:1542
tcp_v4_rcv+0x1a03/0x1bf0 net/ipv4/tcp_ipv4.c:1923
ip_protocol_deliver_rcu+0x51/0x470 net/ipv4/ip_input.c:204
ip_local_deliver_finish+0x110/0x140 net/ipv4/ip_input.c:231
NF_HOOK include/linux/netfilter.h:305 [inline]
NF_HOOK include/linux/netfilter.h:299 [inline]
ip_local_deliver+0x133/0x210 net/ipv4/ip_input.c:252
dst_input include/net/dst.h:442 [inline]
ip_rcv_finish+0x121/0x160 net/ipv4/ip_input.c:413
NF_HOOK include/linux/netfilter.h:305 [inline]
NF_HOOK include/linux/netfilter.h:299 [inline]
ip_rcv+0x18f/0x1a0 net/ipv4/ip_input.c:523

read to 0xffff8881232b8650 of 8 bytes by task 7284 on cpu 1:
list_empty_careful include/linux/list.h:286 [inline]
ep_events_available fs/eventpoll.c:380 [inline]
ep_poll+0x98/0x900 fs/eventpoll.c:1861
do_epoll_wait+0x162/0x180 fs/eventpoll.c:2294
__do_sys_epoll_pwait fs/eventpoll.c:2325 [inline]
__se_sys_epoll_pwait fs/eventpoll.c:2311 [inline]
__x64_sys_epoll_pwait+0xcd/0x170 fs/eventpoll.c:2311
do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7284 Comm: syz-fuzzer Not tainted 5.3.0+ #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.