[moderation] [fs?] KCSAN: data-race in ep_modify / ep_poll_callback (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c85af715cac0 Merge tag 'vboxsf-v6.9-1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123f0aa9180000
kernel config: https://syzkaller.appspot.com/x/.config?x=d024e89f7bb376ce
dashboard link: https://syzkaller.appspot.com/bug?extid=f8da2856d9b3d5aa118f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cb8a24fb67ab/disk-c85af715.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/58c43ae1e149/vmlinux-c85af715.xz
kernel image: https://storage.googleapis.com/syzbot-assets/70be5623c16c/bzImage-c85af715.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8da28...@syzkaller.appspotmail.com

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

write to 0xffff88815ff13a68 of 4 bytes by task 9851 on cpu 1:
ep_modify+0x51/0x410 fs/eventpoll.c:1724
do_epoll_ctl+0x4ee/0x950 fs/eventpoll.c:2349
__do_sys_epoll_ctl fs/eventpoll.c:2386 [inline]
__se_sys_epoll_ctl fs/eventpoll.c:2377 [inline]
__x64_sys_epoll_ctl+0xc6/0xf0 fs/eventpoll.c:2377
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x72/0x7a

read to 0xffff88815ff13a68 of 4 bytes by task 6980 on cpu 0:
ep_poll_callback+0x4a8/0x5b0 fs/eventpoll.c:1351
__wake_up_common kernel/sched/wait.c:89 [inline]
__wake_up_common_lock kernel/sched/wait.c:106 [inline]
__wake_up+0x65/0xb0 kernel/sched/wait.c:127
ucma_event_handler+0x335/0x4d0 drivers/infiniband/core/ucma.c:356
cma_cm_event_handler+0x30/0x1f0 drivers/infiniband/core/cma.c:2152
addr_handler+0x1da/0x290 drivers/infiniband/core/cma.c:3515
process_one_req+0x207/0x2f0 drivers/infiniband/core/addr.c:646
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
worker_thread+0x526/0x730 kernel/workqueue.c:3416
kthread+0x1d1/0x210 kernel/kthread.c:388
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

value changed: 0x00000018 -> 0x0000001b

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6980 Comm: kworker/u8:6 Tainted: G W 6.9.0-rc2-syzkaller-00080-gc85af715cac0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: ib_addr process_one_req
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup