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+109584edb0b8511d7dad at 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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