From: Andrii Nakryiko Date: Sat, 2 Dec 2023 17:56:57 +0000 (-0800) Subject: bpf: enforce precision of R0 on callback return X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0acd03a5bd188b0c501d285d938439618bd855c4;p=linux.git bpf: enforce precision of R0 on callback return Given verifier checks actual value, r0 has to be precise, so we need to propagate precision properly. r0 also has to be marked as read, otherwise subsequent state comparisons will ignore such register as unimportant and precision won't really help here. Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Acked-by: Eduard Zingerman Acked-by: Shung-Hsi Yu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20231202175705.885270-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 25b9d470957ea..849fbf47b5f35 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9590,6 +9590,13 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) verbose(env, "R0 not a scalar value\n"); return -EACCES; } + + /* we are going to rely on register's precise value */ + err = mark_reg_read(env, r0, r0->parent, REG_LIVE_READ64); + err = err ?: mark_chain_precision(env, BPF_REG_0); + if (err) + return err; + if (!tnum_in(range, r0->var_off)) { verbose_invalid_scalar(env, r0, &range, "callback return", "R0"); return -EINVAL;