KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject

KCSAN: data-race in ktime_get_real_seconds / timekeeping_inject_offset
Status: auto-closed as invalid on 2020/08/23 09:27
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 402d, last: 378d

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 (2)				62	4d19h	236d	0/22	moderation: reported on 2020/12/07 11:41

Sample crash report:

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

write to 0xffffffff892c3df8 of 8 bytes by task 26528 on cpu 1:
 tk_xtime_add kernel/time/timekeeping.c:124 [inline]
 timekeeping_inject_offset+0x453/0x6d0 kernel/time/timekeeping.c:1295
 do_adjtimex+0x57e/0x670 kernel/time/timekeeping.c:2332
 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+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff892c3df8 of 8 bytes by task 26529 on cpu 0:
 ktime_get_real_seconds+0x11/0x20 kernel/time/timekeeping.c:939
 recently_deleted fs/ext4/ialloc.c:699 [inline]
 find_inode_bit+0x231/0x3a0 fs/ext4/ialloc.c:724
 __ext4_new_inode+0xc84/0x2fc0 fs/ext4/ialloc.c:927
 ext4_symlink+0x354/0x7e0 fs/ext4/namei.c:3303
 vfs_symlink+0x218/0x2f0 fs/namei.c:3953
 do_symlinkat+0xee/0x280 fs/namei.c:3980
 __do_sys_symlink fs/namei.c:3999 [inline]
 __se_sys_symlink fs/namei.c:3997 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:3997
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26529 Comm: syz-executor.2 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report
ci2-upstream-kcsan-gce	2020/07/19 09:25	upstream	f932d58abc38	9c812472	.config	log	report
ci2-upstream-kcsan-gce	2020/07/16 09:50	upstream	994e99a96c9b	ada108d0	.config	log	report
ci2-upstream-kcsan-gce	2020/06/24 15:38	upstream	3e08a95294a4	41694dbf	.config	log	report