Commit 48946bd6 authored Dec 16, 2021 by Hao Luo Committed by Alexei Starovoitov Dec 18, 2021

bpf: Replace ARG_XXX_OR_NULL with ARG_XXX | PTR_MAYBE_NULL



We have introduced a new type to make bpf_arg composable, by
reserving high bits of bpf_arg to represent flags of a type.

One of the flags is PTR_MAYBE_NULL which indicates a pointer
may be NULL. When applying this flag to an arg_type, it means
the arg can take NULL pointer. This patch switches the
qualified arg_types to use this flag. The arg_types changed
in this patch include:

1. ARG_PTR_TO_MAP_VALUE_OR_NULL
2. ARG_PTR_TO_MEM_OR_NULL
3. ARG_PTR_TO_CTX_OR_NULL
4. ARG_PTR_TO_SOCKET_OR_NULL
5. ARG_PTR_TO_ALLOC_MEM_OR_NULL
6. ARG_PTR_TO_STACK_OR_NULL

This patch does not eliminate the use of these arg_types, instead
it makes them an alias to the 'ARG_XXX | PTR_MAYBE_NULL'.

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-3-haoluo@google.com

parent d639b9d1

include/linux/bpf.h

+9 −6

Original line number	Diff line number	Diff line
		@@ -331,13 +331,11 @@ enum bpf_arg_type {
		ARG_PTR_TO_MAP_KEY, /* pointer to stack used as map key */
		ARG_PTR_TO_MAP_VALUE, /* pointer to stack used as map value */
		ARG_PTR_TO_UNINIT_MAP_VALUE, /* pointer to valid memory used to store a map value */
		ARG_PTR_TO_MAP_VALUE_OR_NULL, /* pointer to stack used as map value or NULL */

		/* the following constraints used to prototype bpf_memcmp() and other
		* functions that access data on eBPF program stack
		*/
		ARG_PTR_TO_MEM, /* pointer to valid memory (stack, packet, map value) */
		ARG_PTR_TO_MEM_OR_NULL, /* pointer to valid memory or NULL */
		ARG_PTR_TO_UNINIT_MEM, /* pointer to memory does not need to be initialized,
		* helper function must fill all bytes or clear
		* them in error case.
		@@ -347,26 +345,31 @@ enum bpf_arg_type {
		ARG_CONST_SIZE_OR_ZERO, /* number of bytes accessed from memory or 0 */

		ARG_PTR_TO_CTX, /* pointer to context */
		ARG_PTR_TO_CTX_OR_NULL, /* pointer to context or NULL */
		ARG_ANYTHING, /* any (initialized) argument is ok */
		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 */
		ARG_PTR_TO_LONG, /* pointer to long */
		ARG_PTR_TO_SOCKET, /* pointer to bpf_sock (fullsock) */
		ARG_PTR_TO_SOCKET_OR_NULL, /* pointer to bpf_sock (fullsock) or NULL */
		ARG_PTR_TO_BTF_ID, /* pointer to in-kernel struct */
		ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */
		ARG_PTR_TO_ALLOC_MEM_OR_NULL, /* pointer to dynamically allocated memory or NULL */
		ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */
		ARG_PTR_TO_BTF_ID_SOCK_COMMON, /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
		ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */
		ARG_PTR_TO_FUNC, /* pointer to a bpf program function */
		ARG_PTR_TO_STACK_OR_NULL, /* pointer to stack or NULL */
		ARG_PTR_TO_STACK, /* pointer to stack */
		ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */
		ARG_PTR_TO_TIMER, /* pointer to bpf_timer */
		__BPF_ARG_TYPE_MAX,

		/* Extended arg_types. */
		ARG_PTR_TO_MAP_VALUE_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_MAP_VALUE,
		ARG_PTR_TO_MEM_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_MEM,
		ARG_PTR_TO_CTX_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_CTX,
		ARG_PTR_TO_SOCKET_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_SOCKET,
		ARG_PTR_TO_ALLOC_MEM_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_ALLOC_MEM,
		ARG_PTR_TO_STACK_OR_NULL = PTR_MAYBE_NULL \| ARG_PTR_TO_STACK,

		/* This must be the last entry. Its purpose is to ensure the enum is
		* wide enough to hold the higher bits reserved for bpf_type_flag.
		*/

kernel/bpf/verifier.c

+14 −25

Original line number	Diff line number	Diff line
		@@ -475,14 +475,9 @@ static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
		return type == ARG_PTR_TO_SOCK_COMMON;
		}

		static bool arg_type_may_be_null(enum bpf_arg_type type)
		static bool type_may_be_null(u32 type)
		{
		return type == ARG_PTR_TO_MAP_VALUE_OR_NULL \|\|
		type == ARG_PTR_TO_MEM_OR_NULL \|\|
		type == ARG_PTR_TO_CTX_OR_NULL \|\|
		type == ARG_PTR_TO_SOCKET_OR_NULL \|\|
		type == ARG_PTR_TO_ALLOC_MEM_OR_NULL \|\|
		type == ARG_PTR_TO_STACK_OR_NULL;
		return type & PTR_MAYBE_NULL;
		}

		/* Determine whether the function releases some resources allocated by another
		@@ -5016,9 +5011,8 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,

		static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
		{
		return type == ARG_PTR_TO_MEM \|\|
		type == ARG_PTR_TO_MEM_OR_NULL \|\|
		type == ARG_PTR_TO_UNINIT_MEM;
		return base_type(type) == ARG_PTR_TO_MEM \|\|
		base_type(type) == ARG_PTR_TO_UNINIT_MEM;
		}

		static bool arg_type_is_mem_size(enum bpf_arg_type type)
		@@ -5155,31 +5149,26 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
		[ARG_PTR_TO_MAP_KEY] = &map_key_value_types,
		[ARG_PTR_TO_MAP_VALUE] = &map_key_value_types,
		[ARG_PTR_TO_UNINIT_MAP_VALUE] = &map_key_value_types,
		[ARG_PTR_TO_MAP_VALUE_OR_NULL] = &map_key_value_types,
		[ARG_CONST_SIZE] = &scalar_types,
		[ARG_CONST_SIZE_OR_ZERO] = &scalar_types,
		[ARG_CONST_ALLOC_SIZE_OR_ZERO] = &scalar_types,
		[ARG_CONST_MAP_PTR] = &const_map_ptr_types,
		[ARG_PTR_TO_CTX] = &context_types,
		[ARG_PTR_TO_CTX_OR_NULL] = &context_types,
		[ARG_PTR_TO_SOCK_COMMON] = &sock_types,
		#ifdef CONFIG_NET
		[ARG_PTR_TO_BTF_ID_SOCK_COMMON] = &btf_id_sock_common_types,
		#endif
		[ARG_PTR_TO_SOCKET] = &fullsock_types,
		[ARG_PTR_TO_SOCKET_OR_NULL] = &fullsock_types,
		[ARG_PTR_TO_BTF_ID] = &btf_ptr_types,
		[ARG_PTR_TO_SPIN_LOCK] = &spin_lock_types,
		[ARG_PTR_TO_MEM] = &mem_types,
		[ARG_PTR_TO_MEM_OR_NULL] = &mem_types,
		[ARG_PTR_TO_UNINIT_MEM] = &mem_types,
		[ARG_PTR_TO_ALLOC_MEM] = &alloc_mem_types,
		[ARG_PTR_TO_ALLOC_MEM_OR_NULL] = &alloc_mem_types,
		[ARG_PTR_TO_INT] = &int_ptr_types,
		[ARG_PTR_TO_LONG] = &int_ptr_types,
		[ARG_PTR_TO_PERCPU_BTF_ID] = &percpu_btf_ptr_types,
		[ARG_PTR_TO_FUNC] = &func_ptr_types,
		[ARG_PTR_TO_STACK_OR_NULL] = &stack_ptr_types,
		[ARG_PTR_TO_STACK] = &stack_ptr_types,
		[ARG_PTR_TO_CONST_STR] = &const_str_ptr_types,
		[ARG_PTR_TO_TIMER] = &timer_types,
		};
		@@ -5193,7 +5182,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
		const struct bpf_reg_types *compatible;
		int i, j;

		compatible = compatible_reg_types[arg_type];
		compatible = compatible_reg_types[base_type(arg_type)];
		if (!compatible) {
		verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);
		return -EFAULT;
		@@ -5274,15 +5263,14 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
		return -EACCES;
		}

		if (arg_type == ARG_PTR_TO_MAP_VALUE \|\|
		arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE \|\|
		arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) {
		if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE \|\|
		base_type(arg_type) == ARG_PTR_TO_UNINIT_MAP_VALUE) {
		err = resolve_map_arg_type(env, meta, &arg_type);
		if (err)
		return err;
		}

		if (register_is_null(reg) && arg_type_may_be_null(arg_type))
		if (register_is_null(reg) && type_may_be_null(arg_type))
		/* A NULL register has a SCALAR_VALUE type, so skip
		* type checking.
		*/
		@@ -5351,10 +5339,11 @@ 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 (arg_type == ARG_PTR_TO_MAP_VALUE \|\|
		(arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL &&
		!register_is_null(reg)) \|\|
		arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
		} else if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE \|\|
		base_type(arg_type) == ARG_PTR_TO_UNINIT_MAP_VALUE) {
		if (type_may_be_null(arg_type) && register_is_null(reg))
		return 0;

		/* bpf_map_xxx(..., map_ptr, ..., value) call:
		* check [value, value + map->value_size) validity
		*/