netdev - [PATCH net] bpf/verifier: reject invalid LD_ABS

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Message-ID: <1460481979-1771165-1-git-send-email-ast@fb.com>
Date:	Tue, 12 Apr 2016 10:26:19 -0700
From:	Alexei Starovoitov <ast@...com>
To:	"David S . Miller" <davem@...emloft.net>
CC:	Daniel Borkmann <daniel@...earbox.net>, <netdev@...r.kernel.org>
Subject: [PATCH net] bpf/verifier: reject invalid LD_ABS | BPF_DW instruction

verifier must check for reserved size bits in instruction opcode and
reject BPF_LD | BPF_ABS | BPF_DW and BPF_LD | BPF_IND | BPF_DW instructions,
otherwise interpreter will WARN_RATELIMIT on them during execution.

Fixes: ddd872bc3098 ("bpf: verifier: add checks for BPF_ABS | BPF_IND instructions")
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2e08f8e9b771..618ef77c302a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1374,6 +1374,7 @@ static int check_ld_abs(struct verifier_env *env, struct bpf_insn *insn)
 	}

 	if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
+	    BPF_SIZE(insn->code) == BPF_DW ||
 	    (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
 		verbose("BPF_LD_ABS uses reserved fields\n");
 		return -EINVAL;
-- 
2.8.0