KCSAN: data-race in evict / insert_inode_locked

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 245a4300 Merge branch 'rcu/kcsan' into tip/locking/kcsan
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=13c24421e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a4b9db179318d21f
dashboard link: https://syzkaller.appspot.com/bug?extid=2cb6b1368416ed3cc4c1
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk el...@google.com]

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+2cb6b1...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in evict / insert_inode_locked

write to 0xffff888128f59848 of 8 bytes by task 12347 on cpu 1:
hlist_add_head include/linux/list.h:787 [inline]
insert_inode_locked+0x2db/0x3b0 fs/inode.c:1474
__ext4_new_inode+0x17e7/0x2f10 fs/ext4/ialloc.c:1102
ext4_symlink+0x31c/0x9b0 fs/ext4/namei.c:3275
vfs_symlink fs/namei.c:4131 [inline]
vfs_symlink+0x218/0x310 fs/namei.c:4117
do_symlinkat+0x1a5/0x1e0 fs/namei.c:4158
__do_sys_symlink fs/namei.c:4177 [inline]
__se_sys_symlink fs/namei.c:4175 [inline]
__x64_sys_symlink+0x3f/0x50 fs/namei.c:4175
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888128f59848 of 8 bytes by task 7968 on cpu 0:
inode_unhashed include/linux/fs.h:749 [inline]
remove_inode_hash include/linux/fs.h:3078 [inline]
evict+0x2a0/0x410 fs/inode.c:584
iput_final fs/inode.c:1563 [inline]
iput+0x371/0x4e0 fs/inode.c:1589
do_unlinkat+0x378/0x530 fs/namei.c:4073
__do_sys_unlink fs/namei.c:4114 [inline]
__se_sys_unlink fs/namei.c:4112 [inline]
__x64_sys_unlink+0x3b/0x50 fs/namei.c:4112
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7968 Comm: syz-executor.0 Not tainted 5.5.0-rc1-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.