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bpf: Move the PTR_TO_BTF_ID check to check_reg_type() 

check_reg_type() checks whether a reg can be used as an arg of a
func_proto.  For PTR_TO_BTF_ID, the check is actually not
completely done until the reg->btf_id is pointing to a
kernel struct that is acceptable by the func_proto.

Thus, this patch moves the btf_id check into check_reg_type().
"arg_type" and "arg_btf_id" are passed to check_reg_type() instead of
"compatible".  The compatible_reg_types[] usage is localized in
check_reg_type() now.

The "if (!btf_id) verbose(...); " is also removed since it won't happen.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200925000344.3854828-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-09-24 17:03:44 -07:00 committed by Alexei Starovoitov
parent 182bf3f3dd
commit a968d5e277
1 changed files with 31 additions and 29 deletions
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60
kernel/bpf/verifier.c
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@ -4028,19 +4028,27 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
};
static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
const struct bpf_reg_types *compatible)
enum bpf_arg_type arg_type,
const u32 *arg_btf_id)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
enum bpf_reg_type expected, type = reg->type;
const struct bpf_reg_types *compatible;
int i, j;
compatible = compatible_reg_types[arg_type];
if (!compatible) {
verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);
return -EFAULT;
}
for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {
expected = compatible->types[i];
if (expected == NOT_INIT)
break;
if (type == expected)
return 0;
goto found;
}
verbose(env, "R%d type=%s expected=", regno, reg_type_str[type]);
@ -4048,6 +4056,25 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
verbose(env, "%s, ", reg_type_str[compatible->types[j]]);
verbose(env, "%s\n", reg_type_str[compatible->types[j]]);
return -EACCES;
found:
if (type == PTR_TO_BTF_ID) {
if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id,
*arg_btf_id)) {
verbose(env, "R%d is of type %s but %s is expected\n",
regno, kernel_type_name(reg->btf_id),
kernel_type_name(*arg_btf_id));
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
regno);
return -EACCES;
}
}
return 0;
}
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
@ -4057,7 +4084,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
u32 regno = BPF_REG_1 + arg;
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
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;
@ -4097,35 +4123,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
*/
goto skip_type_check;
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);
err = check_reg_type(env, regno, arg_type, fn->arg_btf_id[arg]);
if (err)
return err;
if (type == PTR_TO_BTF_ID) {
const u32 *btf_id = fn->arg_btf_id[arg];
if (!btf_id) {
verbose(env, "verifier internal error: missing BTF ID\n");
return -EFAULT;
}
if (!btf_struct_ids_match(&env->log, reg->off, reg->btf_id, *btf_id)) {
verbose(env, "R%d is of type %s but %s is expected\n",
regno, kernel_type_name(reg->btf_id), kernel_type_name(*btf_id));
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
regno);
return -EACCES;
}
} else if (type == PTR_TO_CTX) {
if (type == PTR_TO_CTX) {
err = check_ctx_reg(env, reg, regno);
if (err < 0)
return err;