Allow dynamic pointers (struct bpf_dynptr_kern *) to be specified as
parameters in kfuncs. Also, ensure that dynamic pointers passed as argument
are valid and initialized, are a pointer to the stack, and of the type
local. More dynamic pointer types can be supported in the future.
To properly detect whether a parameter is of the desired type, introduce
the stringify_struct() macro to compare the returned structure name with
the desired name. In addition, protect against structure renames, by
halting the build with BUILD_BUG_ON(), so that developers have to revisit
the code.
To check if a dynamic pointer passed to the kfunc is valid and initialized,
and if its type is local, export the existing functions
is_dynptr_reg_valid_init() and is_dynptr_type_expected().
Cc: Joanne Koong <joannelkoong@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220920075951.929132-5-roberto.sassu@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
u32 regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno, u32 mem_size);
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg);
+bool is_dynptr_type_expected(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type);
/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */
+/*
+ * Return the name of the passed struct, if exists, or halt the build if for
+ * example the structure gets renamed. In this way, developers have to revisit
+ * the code using that structure name, and update it accordingly.
+ */
+#define stringify_struct(x) \
+ ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
+ __stringify(x); })
+
struct btf;
struct btf_member;
struct btf_type;
if (is_kfunc) {
bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]);
+ bool arg_dynptr = btf_type_is_struct(ref_t) &&
+ !strcmp(ref_tname,
+ stringify_struct(bpf_dynptr_kern));
/* Permit pointer to mem, but only when argument
* type is pointer to scalar, or struct composed
* (recursively) of scalars.
* When arg_mem_size is true, the pointer can be
* void *.
+ * Also permit initialized local dynamic pointers.
*/
if (!btf_type_is_scalar(ref_t) &&
!__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
+ !arg_dynptr &&
(arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
bpf_log(log,
"arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
return -EINVAL;
}
+ if (arg_dynptr) {
+ if (reg->type != PTR_TO_STACK) {
+ bpf_log(log, "arg#%d pointer type %s %s not to stack\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ if (!is_dynptr_reg_valid_init(env, reg)) {
+ bpf_log(log,
+ "arg#%d pointer type %s %s must be valid and initialized\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ if (!is_dynptr_type_expected(env, reg,
+ ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
+ bpf_log(log,
+ "arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ continue;
+ }
+
/* Check for mem, len pair */
if (arg_mem_size) {
if (check_kfunc_mem_size_reg(env, ®s[regno + 1], regno + 1)) {
return true;
}
-static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
- struct bpf_reg_state *reg)
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg)
{
struct bpf_func_state *state = func(env, reg);
int spi = get_spi(reg->off);
return true;
}
-static bool is_dynptr_type_expected(struct bpf_verifier_env *env,
- struct bpf_reg_state *reg,
- enum bpf_arg_type arg_type)
+bool is_dynptr_type_expected(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type)
{
struct bpf_func_state *state = func(env, reg);
enum bpf_dynptr_type dynptr_type;