Message-ID: <20180330182643.3539371-3-kafai@fb.com>
Date:   Fri, 30 Mar 2018 11:26:35 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: [PATCH bpf-next 02/10] bpf: btf: Validate type reference

After collecting all btf_type in the first pass in an earlier patch,
the second pass (in this patch) can validate the reference types
(e.g. the referring type does exist and it does not refer to itself).

While checking the reference type, it also gathers other information (e.g.
the size of an array).  This info will be useful in checking the
struct's members in a later patch.  They will also be useful in doing
pretty print later.

Signed-off-by: Martin KaFai Lau <kafai@...com>
Acked-by: Alexei Starovoitov <ast@...com>
---
 include/linux/btf.h |  37 +++
 kernel/bpf/btf.c    | 666 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 702 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/btf.h

diff --git a/include/linux/btf.h b/include/linux/btf.h
new file mode 100644
index 000000000000..f14b60368753
--- /dev/null
+++ b/include/linux/btf.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2018 Facebook */
+
+#ifndef _LINUX_BTF_H
+#define _LINUX_BTF_H 1
+
+#include <linux/types.h>
+
+struct btf;
+struct btf_type;
+
+/* Figure out the size of a type_id.  If type_id is a modifier
+ * (e.g. const), it will be resolved to find out the type with size.
+ *
+ * For example:
+ * In describing "const void *",  type_id is "const" and "const"
+ * refers to "void *".  The return type will be "void *".
+ *
+ * If type_id is a simple "int", then return type will be "int".
+ *
+ * @btf: struct btf object
+ * @type_id: Find out the size of type_id. The type_id of the return
+ *           type is set to *type_id.
+ * @ret_size: It can be NULL.  If not NULL, the size of the return
+ *            type is set to *ret_size.
+ * Return: The btf_type (resolved to another type with size info if needed).
+ *         NULL is returned if type_id itself does not have size info
+ *         (e.g. void) or it cannot be resolved to another type that
+ *         has size info.
+ *         *type_id and *ret_size will not be changed in the
+ *         NULL return case.
+ */
+const struct btf_type *btf_type_id_size(const struct btf *btf,
+					u32 *type_id,
+					u32 *ret_size);
+
+#endif
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 3454e729e8fd..f0147dd9a3aa 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -105,6 +105,50 @@
  *
  * In the first pass, it still does some verifications (e.g.
  * checking the name is a valid offset to the string section).
+ *
+ * Pass #2
+ * ~~~~~~~
+ * The main focus is to resolve a btf_type that is referring
+ * to another type.
+ *
+ * We have to ensure the referring type:
+ * 1) does exist in the BTF (i.e. in btf->types[])
+ * 2) does not cause a loop:
+ *	struct A {
+ *		struct B b;
+ *	};
+ *
+ *	struct B {
+ *		struct A a;
+ *	};
+ *
+ * btf_type_needs_resolve() decides if a btf_type needs
+ * to be resolved.
+ *
+ * The needs_resolve type implements the "resolve()" ops which
+ * essentially does a DFS and detects backedge.
+ *
+ * During resolve (or DFS), different C types have different
+ * "RESOLVED" conditions.
+ *
+ * When resolving a BTF_KIND_STRUCT, we need to resolve all its
+ * members because a member is always referring to another
+ * type.  A struct's member can be treated as "RESOLVED" if
+ * it is referring to a BTF_KIND_PTR.  Otherwise, the
+ * following valid C struct would be rejected:
+ *
+ *	struct A {
+ *		int m;
+ *		struct A *a;
+ *	};
+ *
+ * When resolving a BTF_KIND_PTR, it needs to keep resolving if
+ * it is referring to another BTF_KIND_PTR.  Otherwise, we cannot
+ * detect a pointer loop, e.g.:
+ * BTF_KIND_CONST -> BTF_KIND_PTR -> BTF_KIND_CONST -> BTF_KIND_PTR +
+ *                        ^                                         |
+ *                        +-----------------------------------------+
+ *
  */
 
 #define BITS_PER_U64 (sizeof(u64) * BITS_PER_BYTE)
@@ -123,12 +167,19 @@
 	     i < btf_type_vlen(struct_type);			\
 	     i++, member++)
 
+#define for_each_member_from(i, from, struct_type, member)		\
+	for (i = from, member = btf_type_member(struct_type) + from;	\
+	     i < btf_type_vlen(struct_type);				\
+	     i++, member++)
+
 struct btf {
 	union {
 		struct btf_header *hdr;
 		void *data;
 	};
 	struct btf_type **types;
+	u32 *resolved_ids;
+	u32 *resolved_sizes;
 	const char *strings;
 	void *nohdr_data;
 	u32 nr_types;
@@ -136,10 +187,42 @@ struct btf {
 	u32 data_size;
 };
 
+enum verifier_phase {
+	CHECK_META,
+	CHECK_TYPE,
+};
+
+struct resolve_vertex {
+	const struct btf_type *t;
+	u32 type_id;
+	u16 next_member;
+};
+
+enum visit_state {
+	NOT_VISITED,
+	VISITED,
+	RESOLVED,
+};
+
+enum resolve_mode {
+	RESOLVE_TBD,	/* To Be Determined */
+	RESOLVE_PTR,	/* Resolving for Pointer */
+	RESOLVE_STRUCT_OR_ARRAY,	/* Resolving for struct/union
+					 * or array
+					 */
+};
+
+#define MAX_RESOLVE_DEPTH 32
+
 struct btf_verifier_env {
 	struct btf *btf;
+	u8 *visit_states;
+	struct resolve_vertex stack[MAX_RESOLVE_DEPTH];
 	struct bpf_verifier_log log;
 	u32 log_type_id;
+	u32 top_stack;
+	enum verifier_phase phase;
+	enum resolve_mode resolve_mode;
 };
 
 static const char * const btf_kind_str[NR_BTF_KINDS] = {
@@ -163,6 +246,8 @@ struct btf_kind_operations {
 	s32 (*check_meta)(struct btf_verifier_env *env,
 			  const struct btf_type *t,
 			  u32 meta_left);
+	int (*resolve)(struct btf_verifier_env *env,
+		       const struct resolve_vertex *v);
 	void (*log_details)(struct btf_verifier_env *env,
 			    const struct btf_type *t);
 };
@@ -170,6 +255,102 @@ struct btf_kind_operations {
 static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
 static struct btf_type btf_void;
 
+static bool btf_type_is_modifier(const struct btf_type *t)
+{
+	/* Some of them is not strictly a C modifier
+	 * but they are grouped into the same bucket
+	 * for BTF concern:
+	 *   A type (t) that refers to another
+	 *   type through t->type AND its size cannot
+	 *   be determined without following the t->type.
+	 *
+	 * ptr does not fall into this bucket
+	 * because its size is always sizeof(void *).
+	 */
+	switch (BTF_INFO_KIND(t->info)) {
+	case BTF_KIND_TYPEDEF:
+	case BTF_KIND_VOLATILE:
+	case BTF_KIND_CONST:
+	case BTF_KIND_RESTRICT:
+		return true;
+	};
+
+	return false;
+}
+
+static bool btf_type_is_void(const struct btf_type *t)
+{
+	/* void => no type and size info.
+	 * Hence, FWD is also treated as void.
+	 */
+	return t == &btf_void || BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
+}
+
+static bool btf_type_is_void_or_null(const struct btf_type *t)
+{
+	return !t || btf_type_is_void(t);
+}
+
+/* union is only a special case of struct:
+ * all its offsetof(member) == 0
+ */
+static bool btf_type_is_struct(const struct btf_type *t)
+{
+	u8 kind = BTF_INFO_KIND(t->info);
+
+	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
+}
+
+static bool btf_type_is_array(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
+}
+
+static bool btf_type_is_ptr(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_PTR;
+}
+
+static bool btf_type_is_int(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_INT;
+}
+
+/* What types need to be resolved?
+ *
+ * btf_type_is_modifier() is an obvious one.
+ *
+ * btf_type_is_struct() because its member refers to
+ * another type (through member->type).
+
+ * btf_type_is_array() because its element (array->type)
+ * refers to another type.  Array can be thought of a
+ * special case of struct while array just has the same
+ * member-type repeated by array->nelems of times.
+ */
+static bool btf_type_needs_resolve(const struct btf_type *t)
+{
+	return btf_type_is_modifier(t) ||
+		btf_type_is_ptr(t) ||
+		btf_type_is_struct(t) ||
+		btf_type_is_array(t);
+}
+
+/* t->size can be used */
+static bool btf_type_has_size(const struct btf_type *t)
+{
+	switch (BTF_INFO_KIND(t->info)) {
+	case BTF_KIND_INT:
+	case BTF_KIND_FLOAT:
+	case BTF_KIND_STRUCT:
+	case BTF_KIND_UNION:
+	case BTF_KIND_ENUM:
+		return true;
+	};
+
+	return false;
+}
+
 static const char *btf_int_encoding_str(u8 encoding)
 {
 	if (encoding == 0)
@@ -232,6 +413,14 @@ static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
 		return "(invalid-name-offset)";
 }
 
+static const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
+{
+	if (type_id > btf->nr_types)
+		return NULL;
+
+	return btf->types[type_id];
+}
+
 __printf(2, 3) static void __btf_verifier_log(struct bpf_verifier_log *log,
 					      const char *fmt, ...)
 {
@@ -306,6 +495,15 @@ static void btf_verifier_log_member(struct btf_verifier_env *env,
 	if (!bpf_verifier_log_needed(log))
 		return;
 
+	/* The CHECK_META phase already did a btf dump.
+	 *
+	 * If member is logged again, it must hit an error in
+	 * parsing this member.  It is useful to print out which
+	 * struct this member belongs to.
+	 */
+	if (env->phase != CHECK_META)
+		btf_verifier_log_type(env, struct_type, NULL);
+
 	__btf_verifier_log(log, "\t%s type_id=%u bits_offset=%u",
 			   btf_name_by_offset(btf, member->name),
 			   member->type, member->offset);
@@ -367,15 +565,176 @@ static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
 static void btf_free(struct btf *btf)
 {
 	kfree(btf->types);
+	kfree(btf->resolved_sizes);
+	kfree(btf->resolved_ids);
 	kfree(btf->data);
 	kfree(btf);
 }
 
+static int env_resolve_init(struct btf_verifier_env *env)
+{
+	struct btf *btf = env->btf;
+	u32 nr_types = btf->nr_types;
+	u32 *resolved_sizes = NULL;
+	u32 *resolved_ids = NULL;
+	u8 *visit_states = NULL;
+
+	/* +1 for btf_void */
+	resolved_sizes = kvzalloc((nr_types + 1) * sizeof(*resolved_sizes),
+				 GFP_KERNEL | __GFP_NOWARN);
+	if (!resolved_sizes)
+		goto nomem;
+
+	resolved_ids = kvzalloc((nr_types + 1) * sizeof(*resolved_ids),
+			       GFP_KERNEL | __GFP_NOWARN);
+	if (!resolved_ids)
+		goto nomem;
+
+	visit_states = kvzalloc((nr_types + 1) * sizeof(*visit_states),
+			       GFP_KERNEL | __GFP_NOWARN);
+	if (!visit_states)
+		goto nomem;
+
+	btf->resolved_sizes = resolved_sizes;
+	btf->resolved_ids = resolved_ids;
+	env->visit_states = visit_states;
+
+	return 0;
+
+nomem:
+	kfree(resolved_sizes);
+	kfree(resolved_ids);
+	kfree(visit_states);
+	return -ENOMEM;
+}
+
 static void btf_verifier_env_free(struct btf_verifier_env *env)
 {
+	kfree(env->visit_states);
 	kfree(env);
 }
 
+static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
+				     const struct btf_type *next_type)
+{
+	switch (env->resolve_mode) {
+	case RESOLVE_TBD:
+		/* int, enum or void is a sink */
+		return !btf_type_needs_resolve(next_type);
+	case RESOLVE_PTR:
+		/* int, enum, void, struct or array is a sink for ptr */
+		return !btf_type_is_modifier(next_type) &&
+			!btf_type_is_ptr(next_type);
+	case RESOLVE_STRUCT_OR_ARRAY:
+		/* int, enum, void or ptr is a sink for struct and array */
+		return !btf_type_is_modifier(next_type) &&
+			!btf_type_is_array(next_type) &&
+			!btf_type_is_struct(next_type);
+	default:
+		BUG_ON(1);
+	};
+}
+
+static bool env_type_is_resolved(const struct btf_verifier_env *env,
+				 u32 type_id)
+{
+	return env->visit_states[type_id] == RESOLVED;
+}
+
+static int env_stack_push(struct btf_verifier_env *env,
+			  const struct btf_type *t, u32 type_id)
+{
+	struct resolve_vertex *v;
+
+	if (env->top_stack == MAX_RESOLVE_DEPTH)
+		return -E2BIG;
+
+	if (env->visit_states[type_id] != NOT_VISITED)
+		return -EEXIST;
+
+	env->visit_states[type_id] = VISITED;
+
+	v = &env->stack[env->top_stack++];
+	v->t = t;
+	v->type_id = type_id;
+	v->next_member = 0;
+
+	if (env->resolve_mode == RESOLVE_TBD) {
+		if (btf_type_is_ptr(t))
+			env->resolve_mode = RESOLVE_PTR;
+		else if (btf_type_is_struct(t) || btf_type_is_array(t))
+			env->resolve_mode = RESOLVE_STRUCT_OR_ARRAY;
+	}
+
+	return 0;
+}
+
+static void env_stack_set_next_member(struct btf_verifier_env *env,
+				      u16 next_member)
+{
+	env->stack[env->top_stack - 1].next_member = next_member;
+}
+
+static void env_stack_pop_resolved(struct btf_verifier_env *env,
+				   u32 resolved_type_id,
+				   u32 resolved_size)
+{
+	u32 type_id = env->stack[--(env->top_stack)].type_id;
+	struct btf *btf = env->btf;
+
+	btf->resolved_sizes[type_id] = resolved_size;
+	btf->resolved_ids[type_id] = resolved_type_id;
+	env->visit_states[type_id] = RESOLVED;
+}
+
+static const struct resolve_vertex *env_stack_peak(struct btf_verifier_env *env)
+{
+	return env->top_stack ? &env->stack[env->top_stack - 1] : NULL;
+}
+
+/* The input param "type_id" must point to a needs_resolve type */
+static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
+						  u32 *type_id)
+{
+	*type_id = btf->resolved_ids[*type_id];
+	return btf_type_by_id(btf, *type_id);
+}
+
+const struct btf_type *btf_type_id_size(const struct btf *btf,
+					u32 *type_id, u32 *ret_size)
+{
+	const struct btf_type *size_type;
+	u32 size_type_id = *type_id;
+	u32 size = 0;
+
+	size_type = btf_type_by_id(btf, size_type_id);
+	if (btf_type_is_void_or_null(size_type))
+		return NULL;
+
+	if (btf_type_has_size(size_type)) {
+		size = size_type->size;
+	} else if (btf_type_is_array(size_type)) {
+		size = btf->resolved_sizes[size_type_id];
+	} else if (btf_type_is_ptr(size_type)) {
+		size = sizeof(void *);
+	} else {
+		if (WARN_ON_ONCE(!btf_type_is_modifier(size_type)))
+			return NULL;
+
+		size = btf->resolved_sizes[size_type_id];
+		size_type_id = btf->resolved_ids[size_type_id];
+		size_type = btf_type_by_id(btf, size_type_id);
+		if (btf_type_is_void(size_type))
+			return NULL;
+	}
+
+	*type_id = size_type_id;
+	if (ret_size)
+		*ret_size = size;
+
+	return size_type;
+}
+
 static int btf_df_check_meta(struct btf_verifier_env *env,
 			     const struct btf_type *t,
 			     u32 meta_left)
@@ -384,6 +743,13 @@ static int btf_df_check_meta(struct btf_verifier_env *env,
 	return -ENOTSUPP;
 }
 
+static int btf_df_resolve(struct btf_verifier_env *env,
+			  const struct resolve_vertex *v)
+{
+	btf_verifier_log_basic(env, v->t, "Unsupported resolve");
+	return -EINVAL;
+}
+
 static void btf_df_log(struct btf_verifier_env *env,
 		       const struct btf_type *t)
 {
@@ -392,6 +758,7 @@ static void btf_df_log(struct btf_verifier_env *env,
 
 static struct btf_kind_operations df_ops = {
 	.check_meta = btf_df_check_meta,
+	.resolve = btf_df_resolve,
 	.log_details = btf_df_log,
 };
 
@@ -459,6 +826,7 @@ static void btf_int_log(struct btf_verifier_env *env,
 
 const struct btf_kind_operations int_ops = {
 	.check_meta = btf_int_check_meta,
+	.resolve = btf_df_resolve,
 	.log_details = btf_int_log,
 };
 
@@ -481,6 +849,102 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 	return 0;
 }
 
+static int btf_modifier_resolve(struct btf_verifier_env *env,
+				const struct resolve_vertex *v)
+{
+	const struct btf_type *t = v->t;
+	u32 next_type_id = t->type;
+	struct btf *btf = env->btf;
+	const struct btf_type *next_type = btf_type_by_id(btf, next_type_id);
+	u32 next_type_size = 0;
+
+	if (!next_type) {
+		btf_verifier_log_type(env, v->t, "Invalid type_id");
+		return -EINVAL;
+	}
+
+	/* "typedef void new_void", "const void"...etc */
+	if (btf_type_is_void(next_type))
+		goto resolved;
+
+	if (!env_type_is_resolve_sink(env, next_type) &&
+	    !env_type_is_resolved(env, next_type_id))
+		return env_stack_push(env, next_type, next_type_id);
+
+	/* Figure out the resolved next_type_id with size.
+	 * They will be stored in the current modifier's
+	 * resolved_ids and resolved_sizes such that it can
+	 * save us a few type-following when we use it later (e.g. in
+	 * pretty print).
+	 */
+	if (!btf_type_id_size(btf, &next_type_id, &next_type_size) &&
+	    !btf_type_is_void(btf_type_id_resolve(btf, &next_type_id))) {
+		btf_verifier_log_type(env, v->t, "Invalid type_id");
+		return -EINVAL;
+	}
+
+resolved:
+	env_stack_pop_resolved(env, next_type_id, next_type_size);
+
+	return 0;
+}
+
+static int btf_ptr_resolve(struct btf_verifier_env *env,
+			   const struct resolve_vertex *v)
+{
+	const struct btf_type *t = v->t;
+	u32 next_type_id = t->type;
+	struct btf *btf = env->btf;
+	const struct btf_type *next_type = btf_type_by_id(btf, next_type_id);
+	u32 next_type_size = 0;
+
+	if (!next_type) {
+		btf_verifier_log_type(env, v->t, "Invalid type_id");
+		return -EINVAL;
+	}
+
+	/* "void *" */
+	if (btf_type_is_void(next_type))
+		goto resolved;
+
+	if (!env_type_is_resolve_sink(env, next_type) &&
+	    !env_type_is_resolved(env, next_type_id))
+		return env_stack_push(env, next_type, next_type_id);
+
+	/* If the modifier was RESOLVED during RESOLVE_STRUCT_OR_ARRAY,
+	 * the modifier may have stopped resolving when it was resolved
+	 * to a ptr (last-resolved-ptr).
+	 *
+	 * We now need to continue from the last-resolved-ptr to
+	 * ensure the last-resolved-ptr will not referring back to
+	 * the currenct ptr (t).
+	 */
+	if (btf_type_is_modifier(next_type)) {
+		const struct btf_type *resolved_type;
+		u32 resolved_type_id;
+
+		resolved_type_id = next_type_id;
+		resolved_type = btf_type_id_resolve(btf, &resolved_type_id);
+
+		if (btf_type_is_ptr(resolved_type) &&
+		    !env_type_is_resolve_sink(env, resolved_type) &&
+		    !env_type_is_resolved(env, resolved_type_id))
+			return env_stack_push(env, resolved_type,
+					      resolved_type_id);
+	}
+
+	if (!btf_type_id_size(btf, &next_type_id, &next_type_size) &&
+	    !btf_type_is_void(btf_type_id_resolve(btf, &next_type_id))) {
+		btf_verifier_log_type(env, v->t, "Invalid type_id");
+		return -EINVAL;
+	}
+
+resolved:
+	env_stack_pop_resolved(env, next_type_id, 0);
+
+	return 0;
+}
+
 static void btf_ref_type_log(struct btf_verifier_env *env,
 			     const struct btf_type *t)
 {
@@ -489,16 +953,19 @@ static void btf_ref_type_log(struct btf_verifier_env *env,
 
 static struct btf_kind_operations modifier_ops = {
 	.check_meta = btf_ref_type_check_meta,
+	.resolve = btf_modifier_resolve,
 	.log_details = btf_ref_type_log,
 };
 
 static struct btf_kind_operations ptr_ops = {
 	.check_meta = btf_ref_type_check_meta,
+	.resolve = btf_ptr_resolve,
 	.log_details = btf_ref_type_log,
 };
 
 static struct btf_kind_operations fwd_ops = {
 	.check_meta = btf_ref_type_check_meta,
+	.resolve = btf_df_resolve,
 	.log_details = btf_ref_type_log,
 };
 
@@ -537,6 +1004,61 @@ static s32 btf_array_check_meta(struct btf_verifier_env *env,
 	return meta_needed;
 }
 
+static int btf_array_resolve(struct btf_verifier_env *env,
+			     const struct resolve_vertex *v)
+{
+	const struct btf_array *array = btf_type_array(v->t);
+	u32 elem_type_id = array->type;
+	struct btf *btf = env->btf;
+	const struct btf_type *elem_type;
+	u32 elem_size;
+
+	elem_type = btf_type_by_id(btf, elem_type_id);
+	if (btf_type_is_void_or_null(elem_type)) {
+		btf_verifier_log_type(env, v->t,
+				      "Invalid elem");
+		return -EINVAL;
+	}
+
+	if (!env_type_is_resolve_sink(env, elem_type) &&
+	    !env_type_is_resolved(env, elem_type_id))
+		return env_stack_push(env, elem_type, elem_type_id);
+
+	elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
+	if (!elem_type) {
+		btf_verifier_log_type(env, v->t, "Invalid elem");
+		return -EINVAL;
+	}
+
+	if (btf_type_is_int(elem_type)) {
+		int int_type_data = btf_type_int(elem_type);
+		u16 nr_bits = BTF_INT_BITS(int_type_data);
+		u16 nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);
+
+		/* Put more restriction on array of int.  The int cannot
+		 * be a bit field and it must be either u8/u16/u32/u64.
+		 */
+		if (BITS_PER_BYTE_MASKED(nr_bits) ||
+		    BTF_INT_OFFSET(int_type_data) ||
+		    (nr_bytes != sizeof(u8) && nr_bytes != sizeof(u16) &&
+		     nr_bytes != sizeof(u32) && nr_bytes != sizeof(u64))) {
+			btf_verifier_log_type(env, v->t,
+					      "Invalid array of int");
+			return -EINVAL;
+		}
+	}
+
+	if (array->nelems && elem_size > U32_MAX / array->nelems) {
+		btf_verifier_log_type(env, v->t,
+				      "Array size overflows U32_MAX");
+		return -EINVAL;
+	}
+
+	env_stack_pop_resolved(env, elem_type_id, elem_size * array->nelems);
+
+	return 0;
+}
+
 static void btf_array_log(struct btf_verifier_env *env,
 			  const struct btf_type *t)
 {
@@ -548,6 +1070,7 @@ static void btf_array_log(struct btf_verifier_env *env,
 
 static struct btf_kind_operations array_ops = {
 	.check_meta = btf_array_check_meta,
+	.resolve = btf_array_resolve,
 	.log_details = btf_array_log,
 };
 
@@ -607,6 +1130,50 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
 	return meta_needed;
 }
 
+static int btf_struct_resolve(struct btf_verifier_env *env,
+			      const struct resolve_vertex *v)
+{
+	const struct btf_member *member;
+	u16 i;
+
+	/* Before continue resolving the next_member,
+	 * ensure the last member is indeed resolved to a
+	 * type with size info.
+	 */
+	if (v->next_member) {
+		const struct btf_member *last_member;
+		u16 last_member_type_id;
+
+		last_member = btf_type_member(v->t) + v->next_member - 1;
+		last_member_type_id = last_member->type;
+		if (WARN_ON_ONCE(!env_type_is_resolved(env,
+						       last_member_type_id)))
+			return -EINVAL;
+	}
+
+	for_each_member_from(i, v->next_member, v->t, member) {
+		u32 member_type_id = member->type;
+		const struct btf_type *member_type = btf_type_by_id(env->btf,
+								member_type_id);
+
+		if (btf_type_is_void_or_null(member_type)) {
+			btf_verifier_log_member(env, v->t, member,
+						"Invalid member");
+			return -EINVAL;
+		}
+
+		if (!env_type_is_resolve_sink(env, member_type) &&
+		    !env_type_is_resolved(env, member_type_id)) {
+			env_stack_set_next_member(env, i + 1);
+			return env_stack_push(env, member_type, member_type_id);
+		}
+	}
+
+	env_stack_pop_resolved(env, 0, 0);
+
+	return 0;
+}
+
 static void btf_struct_log(struct btf_verifier_env *env,
 			   const struct btf_type *t)
 {
@@ -615,6 +1182,7 @@ static void btf_struct_log(struct btf_verifier_env *env,
 
 static struct btf_kind_operations struct_ops = {
 	.check_meta = btf_struct_check_meta,
+	.resolve = btf_struct_resolve,
 	.log_details = btf_struct_log,
 };
 
@@ -665,6 +1233,7 @@ static void btf_enum_log(struct btf_verifier_env *env,
 
 struct btf_kind_operations enum_ops = {
 	.check_meta = btf_enum_check_meta,
+	.resolve = btf_df_resolve,
 	.log_details = btf_enum_log,
 };
 
@@ -743,9 +1312,104 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
 	return 0;
 }
 
+static int btf_resolve(struct btf_verifier_env *env,
+		       const struct btf_type *t, u32 type_id)
+{
+	const struct resolve_vertex *v;
+	int err = 0;
+
+	env->resolve_mode = RESOLVE_TBD;
+	env_stack_push(env, t, type_id);
+	while (!err && (v = env_stack_peak(env))) {
+		env->log_type_id = v->type_id;
+		err = btf_type_ops(v->t)->resolve(env, v);
+	}
+
+	env->log_type_id = type_id;
+	if (err == -E2BIG)
+		btf_verifier_log_type(env, t,
+				      "Exceeded max resolving depth:%u",
+				      MAX_RESOLVE_DEPTH);
+	else if (err == -EEXIST)
+		btf_verifier_log_type(env, t, "Loop detected");
+
+	return err;
+}
+
+static bool btf_resolve_valid(struct btf_verifier_env *env,
+			      const struct btf_type *t,
+			      u32 type_id)
+{
+	struct btf *btf = env->btf;
+
+	if (!env_type_is_resolved(env, type_id))
+		return false;
+
+	if (btf_type_is_struct(t))
+		return !btf->resolved_ids[type_id] &&
+			!btf->resolved_sizes[type_id];
+
+	if (btf_type_is_modifier(t) || btf_type_is_ptr(t)) {
+		t = btf_type_id_resolve(btf, &type_id);
+		return t && !btf_type_is_modifier(t);
+	}
+
+	if (btf_type_is_array(t)) {
+		const struct btf_array *array = btf_type_array(t);
+		const struct btf_type *elem_type;
+		u32 elem_type_id = array->type;
+		u32 elem_size;
+
+		elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
+		return elem_type && !btf_type_is_modifier(elem_type) &&
+			(array->nelems * elem_size ==
+			 btf->resolved_sizes[type_id]);
+	}
+
+	return false;
+}
+
+static int btf_check_all_types(struct btf_verifier_env *env)
+{
+	struct btf *btf = env->btf;
+	u32 type_id;
+	int err;
+
+	err = env_resolve_init(env);
+	if (err)
+		return err;
+
+	env->phase++;
+	for (type_id = 1; type_id <= btf->nr_types; type_id++) {
+		const struct btf_type *t = btf_type_by_id(btf, type_id);
+
+		env->log_type_id = type_id;
+		if (btf_type_needs_resolve(t) &&
+		    !env_type_is_resolved(env, type_id)) {
+			err = btf_resolve(env, t, type_id);
+			if (err)
+				return err;
+		}
+
+		if (btf_type_needs_resolve(t) &&
+		    !btf_resolve_valid(env, t, type_id)) {
+			btf_verifier_log_type(env, t, "Invalid resolve state");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static int btf_parse_type_sec(struct btf_verifier_env *env)
 {
-	return btf_check_all_metas(env);
+	int err;
+
+	err = btf_check_all_metas(env);
+	if (err)
+		return err;
+
+	return btf_check_all_types(env);
 }
 
 static int btf_parse_str_sec(struct btf_verifier_env *env)
-- 
2.9.5

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