Skip to content

Commit

Permalink
bpf: Replace ARG_XXX_OR_NULL with ARG_XXX | PTR_MAYBE_NULL
Browse files Browse the repository at this point in the history 
commit 48946bd upstream.

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
Cc: stable@vger.kernel.org # 5.16.x
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  • Loading branch information
@haoluo1022 @gregkh
haoluo1022 authored and gregkh committed Feb 23, 2022
1 parent 6c1fcae commit bcd98af
Show file tree
Hide file tree
Showing 2 changed files with 23 additions and 31 deletions.
15 changes: 9 additions & 6 deletions include/linux/bpf.h
View file
Expand Up @@ -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.
Expand All @@ -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.
*/
Expand Down
39 changes: 14 additions & 25 deletions kernel/bpf/verifier.c
View file
Expand Up @@ -472,14 +472,9 @@ 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
Expand Down Expand Up @@ -4963,9 +4958,8 @@ 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)
Expand Down Expand Up @@ -5102,31 +5096,26 @@ 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,
};
Expand All @@ -5140,7 +5129,7 @@ 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;
Expand Down Expand Up @@ -5221,15 +5210,14 @@ 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.
*/
Expand Down Expand Up @@ -5298,10 +5286,11 @@ 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
*/
Expand Down

0 comments on commit bcd98af

Please sign in to comment.