From: Martin KaFai Lau <kafai@fb.com>
Date: Wed, 19 Dec 2018 21:01:01 +0000 (-0800)
Subject: bpf: Ensure line_info.insn_off cannot point to insn with zero code
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=fdbaa0beb78b7c8847e261fe2c32816e9d1c54cc;p=openwrt%2Fstaging%2Fblogic.git

bpf: Ensure line_info.insn_off cannot point to insn with zero code

This patch rejects a line_info if the bpf insn code referred by
line_info.insn_off is 0. F.e. a broken userspace tool might generate
a line_info.insn_off that points to the second 8 bytes of a BPF_LD_IMM64.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e0e77ffeefb8..5c64281d566e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4980,6 +4980,14 @@ static int check_btf_line(struct bpf_verifier_env *env,
 			goto err_free;
 		}
 
+		if (!prog->insnsi[linfo[i].insn_off].code) {
+			verbose(env,
+				"Invalid insn code at line_info[%u].insn_off\n",
+				i);
+			err = -EINVAL;
+			goto err_free;
+		}
+
 		if (!btf_name_by_offset(btf, linfo[i].line_off) ||
 		    !btf_name_by_offset(btf, linfo[i].file_name_off)) {
 			verbose(env, "Invalid line_info[%u].line_off or .file_name_off\n", i);