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bpf: Use a table to drive helper arg type checks 

The mapping between bpf_arg_type and bpf_reg_type is encoded in a big
hairy if statement that is hard to follow. The debug output also leaves
to be desired: if a reg_type doesn't match we only print one of the
options, instead printing all the valid ones.

Convert the if statement into a table which is then used to drive type
checking. If none of the reg_types match we print all options, e.g.:

    R2 type=rdonly_buf expected=fp, pkt, pkt_meta, map_value

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-12-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2020-09-21 13:12:27 +01:00 committed by Alexei Starovoitov
parent fd1b0d604c
commit f79e7ea571
2 changed files with 110 additions and 74 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/bpf.h
View File

@ -292,6 +292,7 @@ enum bpf_arg_type {
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 */
__BPF_ARG_TYPE_MAX,
};
/* type of values returned from helper functions */

183
kernel/bpf/verifier.c
View File

@ -3903,12 +3903,6 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type)
type == ARG_CONST_SIZE_OR_ZERO;
}
static bool arg_type_is_alloc_mem_ptr(enum bpf_arg_type type)
{
return type == ARG_PTR_TO_ALLOC_MEM ||
type == ARG_PTR_TO_ALLOC_MEM_OR_NULL;
}
static bool arg_type_is_alloc_size(enum bpf_arg_type type)
{
return type == ARG_CONST_ALLOC_SIZE_OR_ZERO;
@ -3957,14 +3951,115 @@ static int resolve_map_arg_type(struct bpf_verifier_env *env,
return 0;
}
struct bpf_reg_types {
const enum bpf_reg_type types[10];
};
static const struct bpf_reg_types map_key_value_types = {
.types = {
PTR_TO_STACK,
PTR_TO_PACKET,
PTR_TO_PACKET_META,
PTR_TO_MAP_VALUE,
},
};
static const struct bpf_reg_types sock_types = {
.types = {
PTR_TO_SOCK_COMMON,
PTR_TO_SOCKET,
PTR_TO_TCP_SOCK,
PTR_TO_XDP_SOCK,
},
};
static const struct bpf_reg_types mem_types = {
.types = {
PTR_TO_STACK,
PTR_TO_PACKET,
PTR_TO_PACKET_META,
PTR_TO_MAP_VALUE,
PTR_TO_MEM,
PTR_TO_RDONLY_BUF,
PTR_TO_RDWR_BUF,
},
};
static const struct bpf_reg_types int_ptr_types = {
.types = {
PTR_TO_STACK,
PTR_TO_PACKET,
PTR_TO_PACKET_META,
PTR_TO_MAP_VALUE,
},
};
static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
static const struct bpf_reg_types *compatible_reg_types[] = {
[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,
[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,
[__BPF_ARG_TYPE_MAX] = NULL,
};
static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
const struct bpf_reg_types *compatible)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
enum bpf_reg_type expected, type = reg->type;
int i, j;
for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {
expected = compatible->types[i];
if (expected == NOT_INIT)
break;
if (type == expected)
return 0;
}
verbose(env, "R%d type=%s expected=", regno, reg_type_str[type]);
for (j = 0; j + 1 < i; j++)
verbose(env, "%s, ", reg_type_str[compatible->types[j]]);
verbose(env, "%s\n", reg_type_str[compatible->types[j]]);
return -EACCES;
}
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
const struct bpf_func_proto *fn)
{
u32 regno = BPF_REG_1 + arg;
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
enum bpf_reg_type expected_type, type = reg->type;
enum bpf_arg_type arg_type = fn->arg_type[arg];
const struct bpf_reg_types *compatible;
enum bpf_reg_type type = reg->type;
int err = 0;
if (arg_type == ARG_DONTCARE)
@ -4003,72 +4098,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
*/
goto skip_type_check;
if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE ||
arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE ||
arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) {
expected_type = PTR_TO_STACK;
if (!type_is_pkt_pointer(type) &&
type != PTR_TO_MAP_VALUE &&
type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO ||
arg_type == ARG_CONST_ALLOC_SIZE_OR_ZERO) {
expected_type = SCALAR_VALUE;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_MAP_PTR) {
expected_type = CONST_PTR_TO_MAP;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_CTX ||
arg_type == ARG_PTR_TO_CTX_OR_NULL) {
expected_type = PTR_TO_CTX;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_SOCK_COMMON) {
expected_type = PTR_TO_SOCK_COMMON;
/* Any sk pointer can be ARG_PTR_TO_SOCK_COMMON */
if (!type_is_sk_pointer(type))
goto err_type;
} else if (arg_type == ARG_PTR_TO_SOCKET ||
arg_type == ARG_PTR_TO_SOCKET_OR_NULL) {
expected_type = PTR_TO_SOCKET;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_BTF_ID) {
expected_type = PTR_TO_BTF_ID;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
expected_type = PTR_TO_MAP_VALUE;
if (type != expected_type)
goto err_type;
} else if (arg_type_is_mem_ptr(arg_type)) {
expected_type = PTR_TO_STACK;
if (!type_is_pkt_pointer(type) &&
type != PTR_TO_MAP_VALUE &&
type != PTR_TO_MEM &&
type != PTR_TO_RDONLY_BUF &&
type != PTR_TO_RDWR_BUF &&
type != expected_type)
goto err_type;
} else if (arg_type_is_alloc_mem_ptr(arg_type)) {
expected_type = PTR_TO_MEM;
if (type != expected_type)
goto err_type;
} else if (arg_type_is_int_ptr(arg_type)) {
expected_type = PTR_TO_STACK;
if (!type_is_pkt_pointer(type) &&
type != PTR_TO_MAP_VALUE &&
type != expected_type)
goto err_type;
} else {
verbose(env, "unsupported arg_type %d\n", arg_type);
compatible = compatible_reg_types[arg_type];
if (!compatible) {
verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);
return -EFAULT;
}
err = check_reg_type(env, regno, compatible);
if (err)
return err;
if (type == PTR_TO_BTF_ID) {
const u32 *btf_id = fn->arg_btf_id[arg];
@ -4221,10 +4260,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
}
return err;
err_type:
verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[type], reg_type_str[expected_type]);
return -EACCES;
}
static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)