KCSAN: data-race in common_perm_cond / task_dump_owner

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 05f22368 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=155db950e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=109584edb0b8511d7dad
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+109584...@syzkaller.appspotmail.com

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

read to 0xffff888124ca931c of 4 bytes by task 7605 on cpu 0:
common_perm_cond+0x65/0x110 security/apparmor/lsm.c:217
apparmor_inode_getattr+0x2b/0x40 security/apparmor/lsm.c:389
security_inode_getattr+0x9b/0xd0 security/security.c:1222
vfs_getattr+0x2e/0x70 fs/stat.c:115
vfs_statx+0x102/0x190 fs/stat.c:191
vfs_stat include/linux/fs.h:3242 [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+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888124ca931c of 4 bytes by task 7608 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:758 [inline]
d_revalidate fs/namei.c:755 [inline]
lookup_fast+0x6f2/0x700 fs/namei.c:1607
walk_component+0x6d/0xe80 fs/namei.c:1796
link_path_walk.part.0+0x5d3/0xa90 fs/namei.c:2131
link_path_walk fs/namei.c:2062 [inline]
path_openat+0x14f/0x36e0 fs/namei.c:3524
do_filp_open+0x11e/0x1b0 fs/namei.c:3555
do_sys_open+0x3b3/0x4f0 fs/open.c:1097
__do_sys_open fs/open.c:1115 [inline]
__se_sys_open fs/open.c:1110 [inline]
__x64_sys_open+0x55/0x70 fs/open.c:1110
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7608 Comm: ps Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
==================================================================


---
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[Dmitry Vyukov]

On Thu, Oct 24, 2019 at 9:30 AM syzbot
<syzbot+109584...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 05f22368 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=155db950e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
> dashboard link: https://syzkaller.appspot.com/bug?extid=109584edb0b8511d7dad
> 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+109584...@syzkaller.appspotmail.com

This may be pretty bad if I am not missing something, see:
https://groups.google.com/d/msg/syzkaller-bugs/mzwiXt4ml68/GuAUQrWtBQAJ

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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.