KCSAN: data-race in iput / other_inode_match

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 941e0d91 mm, kcsan: Instrument SLAB/SLUB free with ASSERT_..
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1468f591e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b313b4492ea15bae
dashboard link: https://syzkaller.appspot.com/bug?extid=679e196cacc9ff09d39c
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+679e19...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in iput / other_inode_match

write to 0xffff8880b15b2638 of 8 bytes by task 11837 on cpu 1:
iput_final fs/inode.c:1566 [inline]
iput+0x2e6/0x4d0 fs/inode.c:1597
do_unlinkat+0x388/0x550 fs/namei.c:4143
__do_sys_unlink fs/namei.c:4184 [inline]
__se_sys_unlink fs/namei.c:4182 [inline]
__x64_sys_unlink+0x38/0x50 fs/namei.c:4182
do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b15b2638 of 8 bytes by task 10584 on cpu 0:
other_inode_match+0x6a/0x570 fs/ext4/inode.c:4849
find_inode_nowait+0x12f/0x160 fs/inode.c:1445
ext4_update_other_inodes_time fs/ext4/inode.c:4897 [inline]
ext4_do_update_inode fs/ext4/inode.c:5023 [inline]
ext4_mark_iloc_dirty+0x123c/0x1500 fs/ext4/inode.c:5578
ext4_mark_inode_dirty+0xe6/0x420 fs/ext4/inode.c:5771
ext4_add_nondir+0xb6/0x170 fs/ext4/namei.c:2571
ext4_symlink+0x63e/0x9e0 fs/ext4/namei.c:3356
vfs_symlink fs/namei.c:4201 [inline]
vfs_symlink+0x216/0x310 fs/namei.c:4187
do_symlinkat+0x1ac/0x1e0 fs/namei.c:4228
__do_sys_symlink fs/namei.c:4247 [inline]
__se_sys_symlink fs/namei.c:4245 [inline]
__x64_sys_symlink+0x3c/0x50 fs/namei.c:4245
do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10584 Comm: syz-executor.0 Not tainted 5.6.0-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.