From e02590b470e8ecfaa48459db9acc95aa14b1664c Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Thu, 9 Mar 2023 14:41:31 -0800 Subject: [PATCH] UPSTREAM: bpf: take into account liveness when propagating precision [ Upstream commit 52c2b005a3c18c565fc70cfd0ca49375f301e952 ] When doing state comparison, if old state has register that is not marked as REG_LIVE_READ, then we just skip comparison, regardless what's the state of corresponing register in current state. This is because not REG_LIVE_READ register is irrelevant for further program execution and correctness. All good here. But when we get to precision propagation, after two states were declared equivalent, we don't take into account old register's liveness, and thus attempt to propagate precision for register in current state even if that register in old state was not REG_LIVE_READ anymore. This is bad, because register in current state could be anything at all and this could cause -EFAULT due to internal logic bugs. Fix by taking into account REG_LIVE_READ liveness mark to keep the logic in state comparison in sync with precision propagation. Fixes: a3ce685dd01a ("bpf: fix precision tracking") Change-Id: Icf48f9c3d23a1f3d7198e776d34eceb5fd0bffe1 Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20230309224131.57449-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 43df44ab3201..7a38b749692c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9555,7 +9555,8 @@ static int propagate_precision(struct bpf_verifier_env *env, state_reg = state->regs; for (i = 0; i < BPF_REG_FP; i++, state_reg++) { if (state_reg->type != SCALAR_VALUE || - !state_reg->precise) + !state_reg->precise || + !(state_reg->live & REG_LIVE_READ)) continue; if (env->log.level & BPF_LOG_LEVEL2) verbose(env, "frame %d: propagating r%d\n", i, fr); @@ -9569,7 +9570,8 @@ static int propagate_precision(struct bpf_verifier_env *env, continue; state_reg = &state->stack[i].spilled_ptr; if (state_reg->type != SCALAR_VALUE || - !state_reg->precise) + !state_reg->precise || + !(state_reg->live & REG_LIVE_READ)) continue; if (env->log.level & BPF_LOG_LEVEL2) verbose(env, "frame %d: propagating fp%d\n",