KCSAN: data-race in d_set_mounted / dput (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4429f14a Merge tag 'block-5.10-2020-11-07' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12ab5792500000
kernel config: https://syzkaller.appspot.com/x/.config?x=76dfc991796328d4
dashboard link: https://syzkaller.appspot.com/bug?extid=c4ec1fc9b81ad5639b4a
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c4ec1f...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_set_mounted / dput

write to 0xffff8881370759c0 of 4 bytes by task 19157 on cpu 0:
d_set_mounted+0x112/0x190 fs/dcache.c:1459
get_mountpoint+0x1ac/0x2f0 fs/namespace.c:740
lock_mount+0x86/0x1d0 fs/namespace.c:2200
do_loopback fs/namespace.c:2349 [inline]
path_mount+0xbb1/0x1c10 fs/namespace.c:3199
do_mount fs/namespace.c:3218 [inline]
__do_sys_mount fs/namespace.c:3426 [inline]
__se_sys_mount+0x23d/0x2e0 fs/namespace.c:3403
__x64_sys_mount+0x63/0x70 fs/namespace.c:3403
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881370759c0 of 4 bytes by task 19147 on cpu 1:
fast_dput fs/dcache.c:746 [inline]
dput+0x2f/0x420 fs/dcache.c:865
path_put fs/namei.c:496 [inline]
terminate_walk+0x109/0x260 fs/namei.c:593
path_lookupat+0x2c5/0x550 fs/namei.c:2351
filename_lookup+0xf2/0x380 fs/namei.c:2367
user_path_at_empty+0x3b/0x50 fs/namei.c:2647
user_path_at include/linux/namei.h:59 [inline]
path_setxattr+0x4c/0x170 fs/xattr.c:562
__do_sys_setxattr fs/xattr.c:582 [inline]
__se_sys_setxattr fs/xattr.c:578 [inline]
__x64_sys_setxattr+0x69/0x80 fs/xattr.c:578
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19147 Comm: syz-executor.5 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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