KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject

KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset (2)
Status: moderation: reported on 2020/12/07 11:41
Reported-by: syzbot+eb0bb2eb0097bddc9fea@syzkaller.appspotmail.com
First crash: 224d, last: 4d08h

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset				3	275d	300d	0/22	auto-closed as invalid on 2020/08/23 09:27

Sample crash report:

==================================================================
BUG: KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset

write to 0xffffffff84533978 of 8 bytes by task 32707 on cpu 0:
 tk_xtime_add kernel/time/timekeeping.c:144 [inline]
 timekeeping_inject_offset+0x453/0x6d0 kernel/time/timekeeping.c:1364
 do_adjtimex+0x581/0x670 kernel/time/timekeeping.c:2395
 posix_clock_realtime_adj+0x11/0x20 kernel/time/posix-timers.c:191
 do_clock_adjtime kernel/time/posix-timers.c:1109 [inline]
 __do_sys_clock_adjtime kernel/time/posix-timers.c:1121 [inline]
 __se_sys_clock_adjtime kernel/time/posix-timers.c:1112 [inline]
 __x64_sys_clock_adjtime+0x12c/0x1b0 kernel/time/posix-timers.c:1112
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff84533978 of 8 bytes by task 32703 on cpu 1:
 ktime_get_real_seconds+0x11/0x20 kernel/time/timekeeping.c:1008
 recently_deleted fs/ext4/ialloc.c:703 [inline]
 find_inode_bit+0x231/0x3a0 fs/ext4/ialloc.c:728
 __ext4_new_inode+0xc6a/0x2f10 fs/ext4/ialloc.c:1063
 ext4_symlink+0x2c3/0x700 fs/ext4/namei.c:3347
 vfs_symlink+0xbe/0x170 fs/namei.c:4178
 do_symlinkat+0xeb/0x280 fs/namei.c:4208
 __do_sys_symlink fs/namei.c:4229 [inline]
 __se_sys_symlink fs/namei.c:4227 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4227
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 32703 Comm: syz-executor.5 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (16):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Title
ci2-upstream-kcsan-gce	2021/04/16 22:52	upstream	2f7b98d1	7e2b734b	.config	log	report	info	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
ci2-upstream-kcsan-gce	2021/04/12 08:19	upstream	7d900724	6a81331a	.config	log	report	info	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
ci2-upstream-kcsan-gce	2021/04/01 22:45	upstream	ffd9fb54	6a81331a	.config	log	report	info	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
ci2-upstream-kcsan-gce	2021/03/13 19:43	upstream	f296bfd5	4a003785	.config	log	report	info	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
ci2-upstream-kcsan-gce	2021/02/06 21:08	upstream	1e0d27fc	0655e081	.config	log	report	info	KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
ci2-upstream-kcsan-gce	2021/01/10 02:55	upstream	2ff90100	2c1f2513	.config	log	report	info
ci2-upstream-kcsan-gce	2020/12/24 12:08	upstream	58cf05f5	c2c1d1dd	.config	log	report	info
ci2-upstream-kcsan-gce	2020/12/22 02:49	upstream	8653b778	04201c06	.config	log	report	info
ci2-upstream-kcsan-gce	2020/12/19 05:44	upstream	3644e2d2	04201c06	.config	log	report	info
ci2-upstream-kcsan-gce	2020/11/19 17:12	upstream	c2e7554e	0767f13f	.config	log	report	info
ci2-upstream-kcsan-gce	2020/11/02 18:26	upstream	3cea11cd	8bc4594f	.config	log	report	info
ci2-upstream-kcsan-gce	2020/10/29 11:16	upstream	23859ae4	f24824d3	.config	log	report	info
ci2-upstream-kcsan-gce	2020/10/24 11:03	upstream	f11901ed	2bb6666c	.config	log	report	info
ci2-upstream-kcsan-gce	2020/09/23 20:23	upstream	805c6d3c	54289b08	.config	log	report	info
ci2-upstream-kcsan-gce	2020/09/09 18:59	upstream	34d4ddd3	ac7ca78e	.config	log	report
ci2-upstream-kcsan-gce	2020/09/09 03:08	upstream	6f6a73c8	abf9ba4f	.config	log	report