netdev - [PATCH net-next 3/6] bpf: adjust insn_aux

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Message-ID: <1489627604-2288703-4-git-send-email-ast@fb.com>
Date:   Wed, 15 Mar 2017 18:26:41 -0700
From:   Alexei Starovoitov <ast@...com>
To:     "David S . Miller" <davem@...emloft.net>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Fengguang Wu <fengguang.wu@...el.com>,
        <netdev@...r.kernel.org>, <kernel-team@...com>
Subject: [PATCH net-next 3/6] bpf: adjust insn_aux_data when patching insns

convert_ctx_accesses() replaces single bpf instruction with a set of
instructions. Adjust corresponding insn_aux_data while patching.
It's needed to make sure subsequent 'for(all insn)' loops
have matching insn and insn_aux_data.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
 kernel/bpf/verifier.c | 44 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5dfa9b8111da..2990fda1c6a5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3162,6 +3162,41 @@ static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
 			insn->src_reg = 0;
 }
 
+/* single env->prog->insni[off] instruction was replaced with the range
+ * insni[off, off + cnt).  Adjust corresponding insn_aux_data by copying
+ * [0, off) and [off, end) to new locations, so the patched range stays zero
+ */
+static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
+				u32 off, u32 cnt)
+{
+	struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
+
+	if (cnt == 1)
+		return 0;
+	new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len);
+	if (!new_data)
+		return -ENOMEM;
+	memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
+	memcpy(new_data + off + cnt - 1, old_data + off,
+	       sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
+	env->insn_aux_data = new_data;
+	vfree(old_data);
+	return 0;
+}
+
+static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
+					    const struct bpf_insn *patch, u32 len)
+{
+	struct bpf_prog *new_prog;
+
+	new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
+	if (!new_prog)
+		return NULL;
+	if (adjust_insn_aux_data(env, new_prog->len, off, len))
+		return NULL;
+	return new_prog;
+}
+
 /* convert load instructions that access fields of 'struct __sk_buff'
  * into sequence of instructions that access fields of 'struct sk_buff'
  */
@@ -3181,10 +3216,10 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			verbose("bpf verifier is misconfigured\n");
 			return -EINVAL;
 		} else if (cnt) {
-			new_prog = bpf_patch_insn_single(env->prog, 0,
-							 insn_buf, cnt);
+			new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
 			if (!new_prog)
 				return -ENOMEM;
+
 			env->prog = new_prog;
 			delta += cnt - 1;
 		}
@@ -3209,7 +3244,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 		else
 			continue;
 
-		if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX)
+		if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX)
 			continue;
 
 		cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog);
@@ -3218,8 +3253,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			return -EINVAL;
 		}
 
-		new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf,
-						 cnt);
+		new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
 		if (!new_prog)
 			return -ENOMEM;
 
-- 
2.8.0