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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 24 Apr 2023 09:43:03 +0200
Message-ID: <CACT4Y+Z1m2F368m1YLXQQP2TgM_1YSLYjU5z8LFGTjgnyXi8_g@mail.gmail.com>
Subject: Re: [syzbot] [nfc?] KCSAN: data-race in __list_del_entry_valid / nfc_llcp_register_device
To:     syzbot <syzbot+742c192afb1b2a0cbe86@syzkaller.appspotmail.com>
Cc:     davem@davemloft.net, edumazet@google.com,
        krzysztof.kozlowski@linaro.org, kuba@kernel.org,
        linux-kernel@vger.kernel.org, linux-nfc@lists.01.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        syzkaller-bugs@googlegroups.com
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On Mon, 24 Apr 2023 at 09:20, syzbot
<syzbot+742c192afb1b2a0cbe86@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    44149752e998 Merge tag 'cgroup-for-6.3-rc6-fixes' of git:/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1682221fc80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=710057cbb8def08c
> dashboard link: https://syzkaller.appspot.com/bug?extid=742c192afb1b2a0cbe86
> 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/7bfa303f05cc/disk-44149752.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/4e8ea8730409/vmlinux-44149752.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e584bce13ba7/bzImage-44149752.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+742c192afb1b2a0cbe86@syzkaller.appspotmail.com

Concurrent list modifications can lead to arbitrary memory corruptions.

> ==================================================================
> BUG: KCSAN: data-race in __list_del_entry_valid / nfc_llcp_register_device
>
> read to 0xffff88810318c808 of 8 bytes by task 28453 on cpu 1:
>  __list_del_entry_valid+0x15/0xe0 lib/list_debug.c:46
>  __list_del_entry include/linux/list.h:134 [inline]
>  list_del include/linux/list.h:148 [inline]
>  local_release net/nfc/llcp_core.c:172 [inline]
>  kref_put include/linux/kref.h:65 [inline]
>  nfc_llcp_local_put net/nfc/llcp_core.c:182 [inline]
>  nfc_llcp_unregister_device+0x7e/0x130 net/nfc/llcp_core.c:1620
>  nfc_unregister_device+0xe6/0x130 net/nfc/core.c:1179
>  nci_unregister_device+0x14c/0x160 net/nfc/nci/core.c:1303
>  virtual_ncidev_close+0x30/0x50 drivers/nfc/virtual_ncidev.c:163
>  __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
>  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>  exit_to_user_mode_loop+0xd1/0xe0 kernel/entry/common.c:171
>  exit_to_user_mode_prepare+0x6c/0xb0 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
>
> write to 0xffff88810318c808 of 8 bytes by task 28459 on cpu 0:
>  __list_add include/linux/list.h:72 [inline]
>  list_add include/linux/list.h:88 [inline]
>  nfc_llcp_register_device+0x3e4/0x440 net/nfc/llcp_core.c:1604
>  nfc_register_device+0x67/0x190 net/nfc/core.c:1124
>  nci_register_device+0x4e6/0x570 net/nfc/nci/core.c:1257
>  virtual_ncidev_open+0xdc/0x140 drivers/nfc/virtual_ncidev.c:148
>  misc_open+0x1fd/0x230 drivers/char/misc.c:165
>  chrdev_open+0x349/0x3c0 fs/char_dev.c:414
>  do_dentry_open+0x5b3/0x930 fs/open.c:920
>  vfs_open+0x47/0x50 fs/open.c:1051
>  do_open fs/namei.c:3560 [inline]
>  path_openat+0x17e6/0x1d00 fs/namei.c:3715
>  do_filp_open+0xf6/0x200 fs/namei.c:3742
>  do_sys_openat2+0xb5/0x2a0 fs/open.c:1348
>  do_sys_open fs/open.c:1364 [inline]
>  __do_sys_openat fs/open.c:1380 [inline]
>  __se_sys_openat fs/open.c:1375 [inline]
>  __x64_sys_openat+0xf3/0x120 fs/open.c:1375
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> value changed: 0xffffffff85eac670 -> 0xdead000000000122
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 0 PID: 28459 Comm: syz-executor.0 Not tainted 6.3.0-rc6-syzkaller-00138-g44149752e998 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
> ==================================================================
>
>
> ---
> 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.
>
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