Message-Id: <1555106392-20117-8-git-send-email-jiong.wang@netronome.com>
Date:   Fri, 12 Apr 2019 22:59:40 +0100
From:   Jiong Wang <jiong.wang@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        oss-drivers@...ronome.com, Jiong Wang <jiong.wang@...ronome.com>
Subject: [PATCH v3 bpf-next 07/19] bpf: reduce false alarm by refining helper call arg types

Unlike BPF to BPF function call, BPF helper call is calls to native insns
that verifier can't walk. So, verifier needs helper proto type descriptions
for data-flow purpose.

There is such information already, but it is not differentiate sub-register
read with full register read.

This patch split "enum bpf_arg_type" for sub-register read, and updated
descriptions for several functions that shown frequent usage in one Cilium
benchmark.

"is_reg64" then taught about these new arg types.

Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Signed-off-by: Jiong Wang <jiong.wang@...ronome.com>
---
 include/linux/bpf.h   |  3 +++
 kernel/bpf/core.c     |  2 +-
 kernel/bpf/helpers.c  |  2 +-
 kernel/bpf/verifier.c | 61 +++++++++++++++++++++++++++++++++++++++++++--------
 net/core/filter.c     | 28 +++++++++++------------
 5 files changed, 71 insertions(+), 25 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f15432d..884b8e1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -197,9 +197,12 @@ enum bpf_arg_type {
 
 	ARG_CONST_SIZE,		/* number of bytes accessed from memory */
 	ARG_CONST_SIZE_OR_ZERO,	/* number of bytes accessed from memory or 0 */
+	ARG_CONST_SIZE32,	/* Likewise, but size fits into 32-bit */
+	ARG_CONST_SIZE32_OR_ZERO,	/* Ditto */
 
 	ARG_PTR_TO_CTX,		/* pointer to context */
 	ARG_ANYTHING,		/* any (initialized) argument is ok */
+	ARG_ANYTHING32,		/* Likewise, but it is a 32-bit argument */
 	ARG_PTR_TO_SPIN_LOCK,	/* pointer to bpf_spin_lock */
 	ARG_PTR_TO_SOCK_COMMON,	/* pointer to sock_common */
 	ARG_PTR_TO_INT,		/* pointer to int */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index ace8c22..2792eda 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2067,7 +2067,7 @@ const struct bpf_func_proto bpf_tail_call_proto = {
 	.ret_type	= RET_VOID,
 	.arg1_type	= ARG_PTR_TO_CTX,
 	.arg2_type	= ARG_CONST_MAP_PTR,
-	.arg3_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING32,
 };
 
 /* Stub for JITs that only support cBPF. eBPF programs are interpreted.
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4266ffd..039ec8e 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -221,7 +221,7 @@ const struct bpf_func_proto bpf_get_current_comm_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,
-	.arg2_type	= ARG_CONST_SIZE,
+	.arg2_type	= ARG_CONST_SIZE32,
 };
 
 #if defined(CONFIG_QUEUED_SPINLOCKS) || defined(CONFIG_BPF_ARCH_SPINLOCK)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3bcbd9b..83b3f83 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1174,12 +1174,47 @@ static int mark_reg_read(struct bpf_verifier_env *env,
 	return 0;
 }
 
+static bool helper_call_arg64(struct bpf_verifier_env *env, int func_id,
+			      u32 regno)
+{
+	/* get_func_proto must succeed, other it should have been rejected
+	 * early inside check_helper_call.
+	 */
+	const struct bpf_func_proto *fn =
+		env->ops->get_func_proto(func_id, env->prog);
+	enum bpf_arg_type arg_type;
+
+	switch (regno) {
+	case BPF_REG_1:
+		arg_type = fn->arg1_type;
+		break;
+	case BPF_REG_2:
+		arg_type = fn->arg2_type;
+		break;
+	case BPF_REG_3:
+		arg_type = fn->arg3_type;
+		break;
+	case BPF_REG_4:
+		arg_type = fn->arg4_type;
+		break;
+	case BPF_REG_5:
+		arg_type = fn->arg5_type;
+		break;
+	default:
+		arg_type = ARG_DONTCARE;
+	}
+
+	return arg_type != ARG_CONST_SIZE32 &&
+	       arg_type != ARG_CONST_SIZE32_OR_ZERO &&
+	       arg_type != ARG_ANYTHING32;
+}
+
 /* This function is supposed to be used by the following 32-bit optimization
  * code only. It returns TRUE if the source or destination register operates
  * on 64-bit, otherwise return FALSE.
  */
-static bool is_reg64(struct bpf_insn *insn, u32 regno,
-		     struct bpf_reg_state *reg, enum reg_arg_type t)
+static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
+		     u32 regno, struct bpf_reg_state *reg, enum reg_arg_type t)
 {
 	u8 code, class, op;
 
@@ -1201,9 +1236,12 @@ static bool is_reg64(struct bpf_insn *insn, u32 regno,
 			if (insn->src_reg == BPF_PSEUDO_CALL)
 				return false;
 			/* Helper call will reach here because of arg type
-			 * check. Conservatively marking all args as 64-bit.
+			 * check.
 			 */
-			return true;
+			if (t == SRC_OP)
+				return helper_call_arg64(env, insn->imm, regno);
+
+			return false;
 		}
 	}
 
@@ -1283,7 +1321,7 @@ static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
 	}
 
 	reg = &regs[regno];
-	rw64 = is_reg64(insn, regno, reg, t);
+	rw64 = is_reg64(env, insn, regno, reg, t);
 	if (t == SRC_OP) {
 		/* check whether register used as source operand can be read */
 		if (reg->type == NOT_INIT) {
@@ -2576,7 +2614,9 @@ static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
 static bool arg_type_is_mem_size(enum bpf_arg_type type)
 {
 	return type == ARG_CONST_SIZE ||
-	       type == ARG_CONST_SIZE_OR_ZERO;
+	       type == ARG_CONST_SIZE_OR_ZERO ||
+	       type == ARG_CONST_SIZE32 ||
+	       type == ARG_CONST_SIZE32_OR_ZERO;
 }
 
 static bool arg_type_is_int_ptr(enum bpf_arg_type type)
@@ -2610,7 +2650,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 	if (err)
 		return err;
 
-	if (arg_type == ARG_ANYTHING) {
+	if (arg_type == ARG_ANYTHING || arg_type == ARG_ANYTHING32) {
 		if (is_pointer_value(env, regno)) {
 			verbose(env, "R%d leaks addr into helper function\n",
 				regno);
@@ -2633,7 +2673,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 		    type != expected_type)
 			goto err_type;
 	} else if (arg_type == ARG_CONST_SIZE ||
-		   arg_type == ARG_CONST_SIZE_OR_ZERO) {
+		   arg_type == ARG_CONST_SIZE_OR_ZERO ||
+		   arg_type == ARG_CONST_SIZE32 ||
+		   arg_type == ARG_CONST_SIZE32_OR_ZERO) {
 		expected_type = SCALAR_VALUE;
 		if (type != expected_type)
 			goto err_type;
@@ -2733,7 +2775,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 					      meta->map_ptr->value_size, false,
 					      meta);
 	} else if (arg_type_is_mem_size(arg_type)) {
-		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
+		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO ||
+					  arg_type == ARG_CONST_SIZE32_OR_ZERO);
 
 		/* remember the mem_size which may be used later
 		 * to refine return values.
diff --git a/net/core/filter.c b/net/core/filter.c
index 95a27fd..d3c7200 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1694,9 +1694,9 @@ static const struct bpf_func_proto bpf_skb_store_bytes_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_PTR_TO_MEM,
-	.arg4_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_CONST_SIZE32,
 	.arg5_type	= ARG_ANYTHING,
 };
 
@@ -1725,9 +1725,9 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_PTR_TO_UNINIT_MEM,
-	.arg4_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_CONST_SIZE32,
 };
 
 BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb,
@@ -1876,7 +1876,7 @@ static const struct bpf_func_proto bpf_l3_csum_replace_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_ANYTHING,
 	.arg4_type	= ARG_ANYTHING,
 	.arg5_type	= ARG_ANYTHING,
@@ -1929,7 +1929,7 @@ static const struct bpf_func_proto bpf_l4_csum_replace_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_ANYTHING,
 	.arg4_type	= ARG_ANYTHING,
 	.arg5_type	= ARG_ANYTHING,
@@ -1968,9 +1968,9 @@ static const struct bpf_func_proto bpf_csum_diff_proto = {
 	.pkt_access	= true,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_MEM_OR_NULL,
-	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg2_type	= ARG_CONST_SIZE32_OR_ZERO,
 	.arg3_type	= ARG_PTR_TO_MEM_OR_NULL,
-	.arg4_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg4_type	= ARG_CONST_SIZE32_OR_ZERO,
 	.arg5_type	= ARG_ANYTHING,
 };
 
@@ -2151,7 +2151,7 @@ static const struct bpf_func_proto bpf_redirect_proto = {
 	.func           = bpf_redirect,
 	.gpl_only       = false,
 	.ret_type       = RET_INTEGER,
-	.arg1_type      = ARG_ANYTHING,
+	.arg1_type      = ARG_ANYTHING32,
 	.arg2_type      = ARG_ANYTHING,
 };
 
@@ -2929,7 +2929,7 @@ static const struct bpf_func_proto bpf_skb_change_proto_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_ANYTHING,
 };
 
@@ -2949,7 +2949,7 @@ static const struct bpf_func_proto bpf_skb_change_type_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 };
 
 static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
@@ -3241,7 +3241,7 @@ static const struct bpf_func_proto bpf_skb_change_tail_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
-	.arg2_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_ANYTHING32,
 	.arg3_type	= ARG_ANYTHING,
 };
 
@@ -3837,7 +3837,7 @@ static const struct bpf_func_proto bpf_skb_get_tunnel_key_proto = {
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
 	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
-	.arg3_type	= ARG_CONST_SIZE,
+	.arg3_type	= ARG_CONST_SIZE32,
 	.arg4_type	= ARG_ANYTHING,
 };
 
@@ -3946,7 +3946,7 @@ static const struct bpf_func_proto bpf_skb_set_tunnel_key_proto = {
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
 	.arg2_type	= ARG_PTR_TO_MEM,
-	.arg3_type	= ARG_CONST_SIZE,
+	.arg3_type	= ARG_CONST_SIZE32,
 	.arg4_type	= ARG_ANYTHING,
 };
 
-- 
2.7.4

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