Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Date:   Thu, 17 Oct 2019 05:36:08 -0700
Message-ID: <000000000000328b2905951a7667@google.com>
Subject: KCSAN: data-race in task_dump_owner / task_dump_owner
From:   syzbot <syzbot+e392f8008a294fdf8891@syzkaller.appspotmail.com>
To:     adobriyan@gmail.com, akpm@linux-foundation.org,
        casey@schaufler-ca.com, christian@brauner.io, elver@google.com,
        keescook@chromium.org, kent.overstreet@gmail.com,
        khlebnikov@yandex-team.ru, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, mhocko@suse.com, shakeelb@google.com,
        syzkaller-bugs@googlegroups.com, tglx@linutronix.de
Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello,

syzbot found the following crash on:

HEAD commit:    d724f94f x86, kcsan: Enable KCSAN for x86
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=17884db3600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c0906aa620713d80
dashboard link: https://syzkaller.appspot.com/bug?extid=e392f8008a294fdf8891
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e392f8008a294fdf8891@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in task_dump_owner / task_dump_owner

write to 0xffff8881255bb7fc of 4 bytes by task 7804 on cpu 0:
  task_dump_owner+0xd8/0x260 fs/proc/base.c:1742
  pid_update_inode+0x3c/0x70 fs/proc/base.c:1818
  pid_revalidate+0x91/0xd0 fs/proc/base.c:1841
  d_revalidate fs/namei.c:765 [inline]
  d_revalidate fs/namei.c:762 [inline]
  lookup_fast+0x7cb/0x7e0 fs/namei.c:1613
  walk_component+0x6d/0xe80 fs/namei.c:1804
  link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2139
  link_path_walk fs/namei.c:2070 [inline]
  path_openat+0x14f/0x3530 fs/namei.c:3532
  do_filp_open+0x11e/0x1b0 fs/namei.c:3563
  do_sys_open+0x3b3/0x4f0 fs/open.c:1089
  __do_sys_open fs/open.c:1107 [inline]
  __se_sys_open fs/open.c:1102 [inline]
  __x64_sys_open+0x55/0x70 fs/open.c:1102
  do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881255bb7fc of 4 bytes by task 7813 on cpu 1:
  task_dump_owner+0xd8/0x260 fs/proc/base.c:1742
  pid_update_inode+0x3c/0x70 fs/proc/base.c:1818
  pid_revalidate+0x91/0xd0 fs/proc/base.c:1841
  d_revalidate fs/namei.c:765 [inline]
  d_revalidate fs/namei.c:762 [inline]
  lookup_fast+0x7cb/0x7e0 fs/namei.c:1613
  walk_component+0x6d/0xe80 fs/namei.c:1804
  lookup_last fs/namei.c:2271 [inline]
  path_lookupat.isra.0+0x13a/0x5a0 fs/namei.c:2316
  filename_lookup+0x145/0x2d0 fs/namei.c:2346
  user_path_at_empty+0x4c/0x70 fs/namei.c:2606
  user_path_at include/linux/namei.h:60 [inline]
  vfs_statx+0xd9/0x190 fs/stat.c:187
  vfs_stat include/linux/fs.h:3188 [inline]
  __do_sys_newstat+0x51/0xb0 fs/stat.c:341
  __se_sys_newstat fs/stat.c:337 [inline]
  __x64_sys_newstat+0x3a/0x50 fs/stat.c:337
  do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7813 Comm: ps Not tainted 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
==================================================================


---
This bug 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 bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.