KCSAN: data-race in nilfs_attach_log_writer / nilfs_segctor

KCSAN: data-race in nilfs_attach_log_writer / nilfs_segctor_thread
Status: moderation: reported on 2020/12/07 11:44
Reported-by: syzbot+c08a569228495050763c@syzkaller.appspotmail.com
First crash: 94d, last: 29d

Sample crash report:

NILFS (loop2): broken superblock, retrying with spare superblock (blocksize = 2048)
NILFS (loop2): mounting unchecked fs
NILFS (loop2): recovery complete
==================================================================
BUG: KCSAN: data-race in nilfs_attach_log_writer / nilfs_segctor_thread

write to 0xffff8880259189e8 of 8 bytes by task 17367 on cpu 1:
 nilfs_segctor_thread+0x7a/0x700 fs/nilfs2/segment.c:2541
 kthread+0x1fd/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff8880259189e8 of 8 bytes by task 17358 on cpu 0:
 nilfs_segctor_start_thread fs/nilfs2/segment.c:2623 [inline]
 nilfs_attach_log_writer+0x4b3/0x560 fs/nilfs2/segment.c:2785
 nilfs_fill_super fs/nilfs2/super.c:1072 [inline]
 nilfs_mount+0x90b/0xac0 fs/nilfs2/super.c:1316
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x190 fs/super.c:1496
 do_new_mount fs/namespace.c:2878 [inline]
 path_mount+0x119d/0x1c10 fs/namespace.c:3208
 do_mount fs/namespace.c:3221 [inline]
 __do_sys_mount fs/namespace.c:3429 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3406
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3406
 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: 0 PID: 17358 Comm: syz-executor.2 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (7):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Maintainers
ci2-upstream-kcsan-gce	2020/12/26 16:16	upstream	40f78232	821e0b09	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/12/18 03:16	upstream	d64c6f96	04201c06	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/11/15 01:17	upstream	f01c30de	1bf9a662	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/11/14 02:46	upstream	9e6a39ea	1bf9a662	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/11/03 00:02	upstream	495023e4	7f344fa6	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/10/29 10:00	upstream	23859ae4	f24824d3	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org
ci2-upstream-kcsan-gce	2020/10/22 23:20	upstream	96485e44	4e740c00	.config	log	report	info	konishi.ryusuke@gmail.com, linux-kernel@vger.kernel.org, linux-nilfs@vger.kernel.org