KCSAN: data-race in task_dump_owner / task_dump_owner

[syzbot]

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@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
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
==================================================================


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