From 19ceb4178d31e543479d75e20c2f9df08f16632f Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 30 Nov 2017 21:31:37 -0800 Subject: [PATCH] bpf: don't mark FP reg as uninit when verifier hits an internal bug don't mark register R10==FP as uninit, since it's read only register and it's not technically correct to let verifier run further, since it may assume that R10 has valid auxiliary state. While developing subsequent patches this issue was discovered, though the code eventually changed that aux reg state doesn't have pointers any more it is still safer to avoid clearing readonly register. Signed-off-by: Alexei Starovoitov Acked-by: John Fastabend Acked-by: Daniel Borkmann Signed-off-by: Daniel Borkmann --- kernel/bpf/verifier.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f722939..14ad7c6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -584,8 +584,8 @@ static void mark_reg_unknown(struct bpf_verifier_env *env, { if (WARN_ON(regno >= MAX_BPF_REG)) { verbose(env, "mark_reg_unknown(regs, %u)\n", regno); - /* Something bad happened, let's kill all regs */ - for (regno = 0; regno < MAX_BPF_REG; regno++) + /* Something bad happened, let's kill all regs except FP */ + for (regno = 0; regno < BPF_REG_FP; regno++) __mark_reg_not_init(regs + regno); return; } @@ -603,8 +603,8 @@ static void mark_reg_not_init(struct bpf_verifier_env *env, { if (WARN_ON(regno >= MAX_BPF_REG)) { verbose(env, "mark_reg_not_init(regs, %u)\n", regno); - /* Something bad happened, let's kill all regs */ - for (regno = 0; regno < MAX_BPF_REG; regno++) + /* Something bad happened, let's kill all regs except FP */ + for (regno = 0; regno < BPF_REG_FP; regno++) __mark_reg_not_init(regs + regno); return; } -- 2.7.4