[syzbot] [kernel?] KCSAN: data-race in free_pid / zap_pid_ns_processes (5)

[syzbot] [kernel?] KCSAN: data-race in free_pid / zap_pid_ns_processes (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    20cb38a7af88 Merge tag 'for-6.9-rc2-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b8252d180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=624180927e9036c3
dashboard link: https://syzkaller.appspot.com/bug?extid=335b9cda8abe9f28e1a4
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f043ce1e5189/disk-20cb38a7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3313ef4e0ece/vmlinux-20cb38a7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3e166298ab90/bzImage-20cb38a7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+335b9cda8abe9f28e1a4@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff88811257b5c8 of 4 bytes by task 10493 on cpu 1:
 free_pid+0x80/0x170 kernel/pid.c:143
 __change_pid+0x19a/0x1c0 kernel/pid.c:367
 detach_pid+0x1c/0x30 kernel/pid.c:372
 __unhash_process kernel/exit.c:133 [inline]
 __exit_signal kernel/exit.c:202 [inline]
 release_task+0x6e7/0xc30 kernel/exit.c:259
 exit_notify kernel/exit.c:774 [inline]
 do_exit+0xf7d/0x1740 kernel/exit.c:898
 do_group_exit+0x102/0x150 kernel/exit.c:1027
 get_signal+0xf2f/0x1080 kernel/signal.c:2911
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xe2/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

read to 0xffff88811257b5c8 of 4 bytes by task 10223 on cpu 0:
 zap_pid_ns_processes+0x1ec/0x2c0 kernel/pid_namespace.c:249
 find_child_reaper kernel/exit.c:610 [inline]
 forget_original_parent kernel/exit.c:699 [inline]
 exit_notify kernel/exit.c:736 [inline]
 do_exit+0x14b4/0x1740 kernel/exit.c:898
 do_group_exit+0x102/0x150 kernel/exit.c:1027
 get_signal+0xf2f/0x1080 kernel/signal.c:2911
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xe2/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

value changed: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10223 Comm: syz-executor.4 Tainted: G        W          6.9.0-rc3-syzkaller-00011-g20cb38a7af88 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
==================================================================


---
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 syzkaller@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