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bpf: reuse subprog argument parsing logic for subprog call checks 

Remove duplicated BTF parsing logic when it comes to subprog call check.
Instead, use (potentially cached) results of btf_prepare_func_args() to
abstract away expectations of each subprog argument in generic terms
(e.g., "this is pointer to context", or "this is a pointer to memory of
size X"), and then use those simple high-level argument type
expectations to validate actual register states to check if they match
expectations.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231215011334.2307144-6-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-12-14 17:13:29 -08:00 committed by Alexei Starovoitov
parent c5a7244759
commit f18c3d88de
2 changed files with 31 additions and 81 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

110
kernel/bpf/verifier.c
View File

@ -9249,101 +9249,54 @@ err_out:
return err;
}
static int btf_check_func_arg_match(struct bpf_verifier_env *env,
const struct btf *btf, u32 func_id,
struct bpf_reg_state *regs,
bool ptr_to_mem_ok)
static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
const struct btf *btf,
struct bpf_reg_state *regs)
{
enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
struct bpf_subprog_info *sub = subprog_info(env, subprog);
struct bpf_verifier_log *log = &env->log;
const char *func_name, *ref_tname;
const struct btf_type *t, *ref_t;
const struct btf_param *args;
u32 i, nargs, ref_id;
u32 i;
int ret;
t = btf_type_by_id(btf, func_id);
if (!t || !btf_type_is_func(t)) {
/* These checks were already done by the verifier while loading
* struct bpf_func_info or in add_kfunc_call().
*/
bpf_log(log, "BTF of func_id %u doesn't point to KIND_FUNC\n",
func_id);
return -EFAULT;
}
func_name = btf_name_by_offset(btf, t->name_off);
t = btf_type_by_id(btf, t->type);
if (!t || !btf_type_is_func_proto(t)) {
bpf_log(log, "Invalid BTF of func %s\n", func_name);
return -EFAULT;
}
args = (const struct btf_param *)(t + 1);
nargs = btf_type_vlen(t);
if (nargs > MAX_BPF_FUNC_REG_ARGS) {
bpf_log(log, "Function %s has %d > %d args\n", func_name, nargs,
MAX_BPF_FUNC_REG_ARGS);
return -EINVAL;
}
ret = btf_prepare_func_args(env, subprog);
if (ret)
return ret;
/* check that BTF function arguments match actual types that the
* verifier sees.
*/
for (i = 0; i < nargs; i++) {
enum bpf_arg_type arg_type = ARG_DONTCARE;
for (i = 0; i < sub->arg_cnt; i++) {
u32 regno = i + 1;
struct bpf_reg_state *reg = &regs[regno];
struct bpf_subprog_arg_info *arg = &sub->args[i];
t = btf_type_skip_modifiers(btf, args[i].type, NULL);
if (btf_type_is_scalar(t)) {
if (reg->type == SCALAR_VALUE)
continue;
bpf_log(log, "R%d is not a scalar\n", regno);
return -EINVAL;
}
if (!btf_type_is_ptr(t)) {
bpf_log(log, "Unrecognized arg#%d type %s\n",
i, btf_type_str(t));
return -EINVAL;
}
ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
ref_tname = btf_name_by_offset(btf, ref_t->name_off);
ret = check_func_arg_reg_off(env, reg, regno, arg_type);
if (ret < 0)
return ret;
if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
if (arg->arg_type == ARG_ANYTHING) {
if (reg->type != SCALAR_VALUE) {
bpf_log(log, "R%d is not a scalar\n", regno);
return -EINVAL;
}
} else if (arg->arg_type == ARG_PTR_TO_CTX) {
ret = check_func_arg_reg_off(env, reg, regno, ARG_DONTCARE);
if (ret < 0)
return ret;
/* If function expects ctx type in BTF check that caller
* is passing PTR_TO_CTX.
*/
if (reg->type != PTR_TO_CTX) {
bpf_log(log,
"arg#%d expected pointer to ctx, but got %s\n",
i, btf_type_str(t));
bpf_log(log, "arg#%d expects pointer to ctx\n", i);
return -EINVAL;
}
} else if (ptr_to_mem_ok) {
const struct btf_type *resolve_ret;
u32 type_size;
} else if (base_type(arg->arg_type) == ARG_PTR_TO_MEM) {
ret = check_func_arg_reg_off(env, reg, regno, ARG_DONTCARE);
if (ret < 0)
return ret;
resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
if (IS_ERR(resolve_ret)) {
bpf_log(log,
"arg#%d reference type('%s %s') size cannot be determined: %ld\n",
i, btf_type_str(ref_t), ref_tname,
PTR_ERR(resolve_ret));
return -EINVAL;
}
if (check_mem_reg(env, reg, regno, type_size))
if (check_mem_reg(env, reg, regno, arg->mem_size))
return -EINVAL;
} else {
bpf_log(log, "reg type unsupported for arg#%d function %s#%d\n", i,
func_name, func_id);
return -EINVAL;
bpf_log(log, "verifier bug: unrecognized arg#%d type %d\n",
i, arg->arg_type);
return -EFAULT;
}
}
@ -9358,11 +9311,10 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
* Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
*/
static int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
struct bpf_reg_state *regs)
struct bpf_reg_state *regs)
{
struct bpf_prog *prog = env->prog;
struct btf *btf = prog->aux->btf;
bool is_global;
u32 btf_id;
int err;
@ -9376,9 +9328,7 @@ static int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
if (prog->aux->func_info_aux[subprog].unreliable)
return -EINVAL;
is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global);
err = btf_check_func_arg_match(env, subprog, btf, regs);
/* Compiler optimizations can remove arguments from static functions
* or mismatched type can be passed into a global function.
* In such cases mark the function as unreliable from BTF point of view.

2
tools/testing/selftests/bpf/progs/test_global_func5.c
View File

@ -26,7 +26,7 @@ int f3(int val, struct __sk_buff *skb)
}
SEC("tc")
__failure __msg("expected pointer to ctx, but got PTR")
__failure __msg("expects pointer to ctx")
int global_func5(struct __sk_buff *skb)
{
return f1(skb) + f2(2, skb) + f3(3, skb);