[PATCH bpf-next v1] bpf: Tidy up verifier check_func_arg()

[Joanne Koong <joannelkoong@gmail.com>]

This patch does two things:

1. For matching against the arg type, the match should be against the
base type of the arg type, since the arg type can have different
bpf_type_flags set on it.

2. Uses switch casing to improve readability + efficiency.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 kernel/bpf/verifier.c | 66 +++++++++++++++++++++++++------------------
 1 file changed, 38 insertions(+), 28 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 328cfab3af60..26e7e787c20a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5533,17 +5533,6 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type)
 	       type == ARG_CONST_SIZE_OR_ZERO;
 }
 
-static bool arg_type_is_alloc_size(enum bpf_arg_type type)
-{
-	return type == ARG_CONST_ALLOC_SIZE_OR_ZERO;
-}
-
-static bool arg_type_is_int_ptr(enum bpf_arg_type type)
-{
-	return type == ARG_PTR_TO_INT ||
-	       type == ARG_PTR_TO_LONG;
-}
-
 static bool arg_type_is_release(enum bpf_arg_type type)
 {
 	return type & OBJ_RELEASE;
@@ -5929,7 +5918,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		meta->ref_obj_id = reg->ref_obj_id;
 	}
 
-	if (arg_type == ARG_CONST_MAP_PTR) {
+	switch (base_type(arg_type)) {
+	case ARG_CONST_MAP_PTR:
 		/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
 		if (meta->map_ptr) {
 			/* Use map_uid (which is unique id of inner map) to reject:
@@ -5954,7 +5944,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		}
 		meta->map_ptr = reg->map_ptr;
 		meta->map_uid = reg->map_uid;
-	} else if (arg_type == ARG_PTR_TO_MAP_KEY) {
+		break;
+	case ARG_PTR_TO_MAP_KEY:
 		/* bpf_map_xxx(..., map_ptr, ..., key) call:
 		 * check that [key, key + map->key_size) are within
 		 * stack limits and initialized
@@ -5971,7 +5962,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->key_size, false,
 					      NULL);
-	} else if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE) {
+		break;
+	case ARG_PTR_TO_MAP_VALUE:
 		if (type_may_be_null(arg_type) && register_is_null(reg))
 			return 0;
 
@@ -5987,14 +5979,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->value_size, false,
 					      meta);
-	} else if (arg_type == ARG_PTR_TO_PERCPU_BTF_ID) {
+		break;
+	case ARG_PTR_TO_PERCPU_BTF_ID:
 		if (!reg->btf_id) {
 			verbose(env, "Helper has invalid btf_id in R%d\n", regno);
 			return -EACCES;
 		}
 		meta->ret_btf = reg->btf;
 		meta->ret_btf_id = reg->btf_id;
-	} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
+		break;
+	case ARG_PTR_TO_SPIN_LOCK:
 		if (meta->func_id == BPF_FUNC_spin_lock) {
 			if (process_spin_lock(env, regno, true))
 				return -EACCES;
@@ -6005,12 +5999,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			verbose(env, "verifier internal error\n");
 			return -EFAULT;
 		}
-	} else if (arg_type == ARG_PTR_TO_TIMER) {
+		break;
+	case ARG_PTR_TO_TIMER:
 		if (process_timer_func(env, regno, meta))
 			return -EACCES;
-	} else if (arg_type == ARG_PTR_TO_FUNC) {
+		break;
+	case ARG_PTR_TO_FUNC:
 		meta->subprogno = reg->subprogno;
-	} else if (base_type(arg_type) == ARG_PTR_TO_MEM) {
+		break;
+	case ARG_PTR_TO_MEM:
 		/* The access to this pointer is only checked when we hit the
 		 * next is_mem_size argument below.
 		 */
@@ -6020,11 +6017,14 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 						      fn->arg_size[arg], false,
 						      meta);
 		}
-	} else if (arg_type_is_mem_size(arg_type)) {
-		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
-
-		err = check_mem_size_reg(env, reg, regno, zero_size_allowed, meta);
-	} else if (arg_type_is_dynptr(arg_type)) {
+		break;
+	case ARG_CONST_SIZE:
+		err = check_mem_size_reg(env, reg, regno, false, meta);
+		break;
+	case ARG_CONST_SIZE_OR_ZERO:
+		err = check_mem_size_reg(env, reg, regno, true, meta);
+		break;
+	case ARG_PTR_TO_DYNPTR:
 		if (arg_type & MEM_UNINIT) {
 			if (!is_dynptr_reg_valid_uninit(env, reg)) {
 				verbose(env, "Dynptr has to be an uninitialized dynptr\n");
@@ -6058,21 +6058,28 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 				err_extra, arg + 1);
 			return -EINVAL;
 		}
-	} else if (arg_type_is_alloc_size(arg_type)) {
+		break;
+	case ARG_CONST_ALLOC_SIZE_OR_ZERO:
 		if (!tnum_is_const(reg->var_off)) {
 			verbose(env, "R%d is not a known constant'\n",
 				regno);
 			return -EACCES;
 		}
 		meta->mem_size = reg->var_off.value;
-	} else if (arg_type_is_int_ptr(arg_type)) {
+		break;
+	case ARG_PTR_TO_INT:
+	case ARG_PTR_TO_LONG:
+	{
 		int size = int_ptr_type_to_size(arg_type);
 
 		err = check_helper_mem_access(env, regno, size, false, meta);
 		if (err)
 			return err;
 		err = check_ptr_alignment(env, reg, 0, size, true);
-	} else if (arg_type == ARG_PTR_TO_CONST_STR) {
+		break;
+	}
+	case ARG_PTR_TO_CONST_STR:
+	{
 		struct bpf_map *map = reg->map_ptr;
 		int map_off;
 		u64 map_addr;
@@ -6111,9 +6118,12 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			verbose(env, "string is not zero-terminated\n");
 			return -EINVAL;
 		}
-	} else if (arg_type == ARG_PTR_TO_KPTR) {
+		break;
+	}
+	case ARG_PTR_TO_KPTR:
 		if (process_kptr_func(env, regno, meta))
 			return -EACCES;
+		break;
 	}
 
 	return err;
-- 
2.30.2