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The timekeeper update path uses a bulk memcpy() to synchronize the timekeeper structure, which is not guaranteed to be atomic. This allows for torn reads in ktime_get_real_seconds() on 64-bit systems, where the sequence counter protection is bypassed for performance. To prevent reading a torn 64-bit xtime_sec value, enforce atomic-like access by using WRITE_ONCE() for the critical field before the bulk memcpy() in timekeeping_update_from_shadow(). Correspondingly, use READ_ONCE() in ktime_get_real_seconds() to ensure a fresh, consistent load from memory. [ tglx: Format changelog and add comment ] Reported-by: syzbot+72789cd1697965e714ca@syzkaller.appspotmail.com Signed-off-by: Dennis Moshegov <dennis@xzync.uk> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Link: https://patch.msgid.link/20260724154405.70-1-dennis@xzync.uk Closes: https://syzkaller.appspot.com/bug?extid=72789cd1697965e714ca