bpf: don't check spilled reg state for non-STACK_SPILLed type slots

spilled_regs[] state is only used for stack slots of type STACK_SPILL,
never for STACK_MISC. Right now, in states_equal(), even if we have
old and current stack state of type STACK_MISC, we compare spilled_regs[]
for that particular offset. Just skip these like we do everywhere else.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/verifier.c

@@ -2828,6 +2828,8 @@ static bool states_equal(struct bpf_verifier_env *env,
 			return false;
 		if (i % BPF_REG_SIZE)
 			continue;
+		if (old->stack_slot_type[i] != STACK_SPILL)
+			continue;
 		if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
 			   &cur->spilled_regs[i / BPF_REG_SIZE],
 			   sizeof(old->spilled_regs[0])))