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Date:   Fri, 21 Apr 2023 01:18:41 -0700
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Subject: [syzbot] [kernel?] KCSAN: data-race in __fput / __tty_hangup (4)
From:   syzbot <syzbot+b7c3ba8cdc2f6cf83c21@syzkaller.appspotmail.com>
To:     gregkh@linuxfoundation.org, jirislaby@kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    fcd476ea6a88 Merge tag 'urgent-rcu.2023.03.28a' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146618b9c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f7350c77b8056a38
dashboard link: https://syzkaller.appspot.com/bug?extid=b7c3ba8cdc2f6cf83c21
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f3d8ce4faab0/disk-fcd476ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fc53d9dee279/vmlinux-fcd476ea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/22ad755d39b2/bzImage-fcd476ea.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b7c3ba8cdc2f6cf83c21@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __fput / __tty_hangup

write to 0xffff88813b31e828 of 8 bytes by task 17702 on cpu 0:
 __tty_hangup+0x1e2/0x510 drivers/tty/tty_io.c:622
 tty_vhangup+0x17/0x20 drivers/tty/tty_io.c:701
 pty_close+0x262/0x280 drivers/tty/pty.c:79
 tty_release+0x204/0x930 drivers/tty/tty_io.c:1753
 __fput+0x245/0x570 fs/file_table.c:321
 ____fput+0x15/0x20 fs/file_table.c:349
 task_work_run+0x123/0x160 kernel/task_work.c:179
 get_signal+0xe5c/0xfe0 kernel/signal.c:2635
 arch_do_signal_or_restart+0x89/0x2b0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop+0x6d/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6a/0xa0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:297
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813b31e828 of 8 bytes by task 17705 on cpu 1:
 __fput+0x21c/0x570 fs/file_table.c:320
 ____fput+0x15/0x20 fs/file_table.c:349
 task_work_run+0x123/0x160 kernel/task_work.c:179
 get_signal+0xe5c/0xfe0 kernel/signal.c:2635
 arch_do_signal_or_restart+0x89/0x2b0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop+0x6d/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6a/0xa0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:297
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0xffffffff84e91ed0 -> 0xffffffff84e91dc0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17705 Comm: syz-executor.0 Not tainted 6.3.0-rc4-syzkaller-00034-gfcd476ea6a88 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/17/2023
==================================================================


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