[moderation] [kernel?] KCSAN: data-race in ktime_get_coarse_real_ts64 / timekeeping_update_from_shadow (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c21bb4193868 Merge tag 'for_linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10680132580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=50826c1b3fc76e7cc9e9
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [jst...@google.com linux-...@vger.kernel.org sb...@kernel.org tg...@kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d4fbf8fa3d0b/disk-c21bb419.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6a0ac310e2fa/vmlinux-c21bb419.xz
kernel image: https://storage.googleapis.com/syzbot-assets/751285db76d1/bzImage-c21bb419.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+50826c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ktime_get_coarse_real_ts64 / timekeeping_update_from_shadow

write to 0xffffffff893d74c8 of 304 bytes by interrupt on cpu 1:
timekeeping_update_from_shadow+0x40d/0x440 kernel/time/timekeeping.c:835
__timekeeping_advance+0xa68/0xc10 kernel/time/timekeeping.c:2614
timekeeping_advance kernel/time/timekeeping.c:2622 [inline]
update_wall_time+0x21/0x50 kernel/time/timekeeping.c:2632
tick_do_update_jiffies64+0x169/0x1c0 kernel/time/tick-sched.c:149
tick_sched_do_timer kernel/time/tick-sched.c:253 [inline]
tick_nohz_handler+0x88/0x380 kernel/time/tick-sched.c:310
__run_hrtimer kernel/time/hrtimer.c:2032 [inline]
__hrtimer_run_queues+0x1f8/0x510 kernel/time/hrtimer.c:2096
hrtimer_interrupt+0x257/0x810 kernel/time/hrtimer.c:2215
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1062
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
is_atomic kernel/kcsan/core.c:260 [inline]
should_watch kernel/kcsan/core.c:277 [inline]
check_access kernel/kcsan/core.c:752 [inline]
__tsan_memcpy+0x162/0x3c0 kernel/kcsan/core.c:1364
avc_has_perm_noaudit+0x86/0x120 security/selinux/avc.c:1164
selinux_inode_permission+0x4bc/0x740 security/selinux/hooks.c:3280
security_inode_permission+0x69/0xa0 security/security.c:1842
inode_permission+0x1da/0x3b0 fs/namei.c:661
may_open+0x255/0x350 fs/namei.c:4274
do_open fs/namei.c:4698 [inline]
path_openat+0x1a43/0x2000 fs/namei.c:4863
do_file_open+0x16c/0x290 fs/namei.c:4892
do_sys_openat2+0xa0/0x130 fs/open.c:1368
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1385
x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff893d7538 of 4 bytes by task 10852 on cpu 0:
tk_xtime_coarse kernel/time/timekeeping.c:217 [inline]
ktime_get_coarse_real_ts64+0x6b/0xf0 kernel/time/timekeeping.c:2665
audit_get_stamp kernel/audit.c:1893 [inline]
audit_log_start+0x5b7/0x730 kernel/audit.c:1971
common_lsm_audit+0x65/0x230 security/lsm_audit.c:442
slow_avc_audit+0x14c/0x190 security/selinux/avc.c:779
audit_inode_permission+0x119/0x160 security/selinux/hooks.c:3149
selinux_inode_permission+0x66e/0x740 security/selinux/hooks.c:3291
security_inode_permission+0x69/0xa0 security/security.c:1842
inode_permission+0x1da/0x3b0 fs/namei.c:661
may_delete_dentry+0x1b7/0x4b0 fs/namei.c:3697
vfs_unlink+0x43/0x490 fs/namei.c:5493
filename_unlinkat+0x1dc/0x410 fs/namei.c:5585
__do_sys_unlink fs/namei.c:5620 [inline]
__se_sys_unlink+0x2b/0xe0 fs/namei.c:5617
__x64_sys_unlink+0x1f/0x30 fs/namei.c:5617
x64_sys_call+0x2eb6/0x3020 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1df61536 -> 0x1e82e030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10852 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
audit: audit_backlog=65 > audit_backlog_limit=64
audit: audit_lost=34913 audit_rate_limit=0 audit_backlog_limit=64
audit: backlog limit exceeded


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