[moderation] [fs?] KCSAN: data-race in do_epoll_wait / ep_poll_callback (11)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 87adedeba51a Merge tag 'net-6.8-rc7' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13d639e2180000
kernel config: https://syzkaller.appspot.com/x/.config?x=53006d590acdf777
dashboard link: https://syzkaller.appspot.com/bug?extid=86b4d7adeeb367c1d6f7
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/85879d80665b/disk-87adedeb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/594eb01e8ed8/vmlinux-87adedeb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c4cbd4a49e35/bzImage-87adedeb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+86b4d7...@syzkaller.appspotmail.com

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

write to 0xffff88812a9ade68 of 4 bytes by task 6611 on cpu 0:
ep_send_events fs/eventpoll.c:1744 [inline]
ep_poll fs/eventpoll.c:1863 [inline]
do_epoll_wait+0x805/0xe70 fs/eventpoll.c:2317
do_epoll_pwait fs/eventpoll.c:2351 [inline]
__do_sys_epoll_pwait fs/eventpoll.c:2364 [inline]
__se_sys_epoll_pwait+0x15f/0x280 fs/eventpoll.c:2358
__x64_sys_epoll_pwait+0x78/0x90 fs/eventpoll.c:2358
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88812a9ade68 of 4 bytes by task 6625 on cpu 1:
ep_poll_callback+0x157/0x5a0 fs/eventpoll.c:1185
__wake_up_common kernel/sched/wait.c:89 [inline]
__wake_up_common_lock kernel/sched/wait.c:106 [inline]
__wake_up_sync_key+0x50/0x80 kernel/sched/wait.c:173
unix_write_space+0xcd/0x140 net/unix/af_unix.c:549
sock_wfree+0x11b/0x330 net/core/sock.c:2480
unix_destruct_scm+0x12e/0x160 net/unix/scm.c:151
skb_release_head_state+0xb7/0x1a0 net/core/skbuff.c:1080
skb_release_all net/core/skbuff.c:1092 [inline]
__kfree_skb+0x16/0x140 net/core/skbuff.c:1108
kfree_skb_reason+0xb0/0x2b0 net/core/skbuff.c:1144
kfree_skb include/linux/skbuff.h:1244 [inline]
unix_release_sock+0x63d/0x780 net/unix/af_unix.c:661
unix_release+0x52/0x70 net/unix/af_unix.c:1051
__sock_release net/socket.c:659 [inline]
sock_close+0x64/0x140 net/socket.c:1421
__fput+0x299/0x630 fs/file_table.c:376
____fput+0x15/0x20 fs/file_table.c:404
task_work_run+0x135/0x1a0 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:108 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
syscall_exit_to_user_mode+0xbd/0x120 kernel/entry/common.c:212
do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x6000001c -> 0x60000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6625 Comm: syz-executor.3 Tainted: G W 6.8.0-rc6-syzkaller-00120-g87adedeba51a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================


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