u32 ip_idents_reserve(u32 hash, int segs)
{
	u32 *p_tstamp = ip_tstamps + hash % IP_IDENTS_SZ;
	atomic_t *p_id = ip_idents + hash % IP_IDENTS_SZ;
	u32 old = ACCESS_ONCE(*p_tstamp);
	u32 now = (u32)jiffies;
	u32 new, delta = 0;

	if (old != now && cmpxchg(p_tstamp, old, now) == old)
		delta = prandom_u32_max(now - old);

	/* Do not use atomic_add_return() as it makes UBSAN unhappy */
	do {
		old = (u32)atomic_read(p_id);
		new = old + delta + segs;
	} while (atomic_cmpxchg(p_id, old, new) != old);

	return new - segs;
}

The product dereferences a pointer that it expects to be valid but is NULL.