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authorKumar Kartikeya Dwivedi <memxor@gmail.com>2022-11-18 04:56:04 +0300
committerAlexei Starovoitov <ast@kernel.org>2022-11-18 06:22:14 +0300
commitac9f06050a3580cf4076a57a470cd71f12a81171 (patch)
tree7bd331dc4f348eb14778aa3b9062e3d028717625 /kernel
parent958cf2e273f0929c66169e0788031310e8118722 (diff)
downloadlinux-ac9f06050a3580cf4076a57a470cd71f12a81171.tar.xz
bpf: Introduce bpf_obj_drop
Introduce bpf_obj_drop, which is the kfunc used to free allocated objects (allocated using bpf_obj_new). Pairing with bpf_obj_new, it implicitly destructs the fields part of object automatically without user intervention. Just like the previous patch, btf_struct_meta that is needed to free up the special fields is passed as a hidden argument to the kfunc. For the user, a convenience macro hides over the kernel side kfunc which is named bpf_obj_drop_impl. Continuing the previous example: void prog(void) { struct foo *f; f = bpf_obj_new(typeof(*f)); if (!f) return; bpf_obj_drop(f); } Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20221118015614.2013203-15-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/helpers.c11
-rw-r--r--kernel/bpf/verifier.c66
2 files changed, 66 insertions, 11 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index c4f1c22cc44c..71d803ca0c1d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1770,6 +1770,16 @@ void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
return p;
}
+void bpf_obj_drop_impl(void *p__alloc, void *meta__ign)
+{
+ struct btf_struct_meta *meta = meta__ign;
+ void *p = p__alloc;
+
+ if (meta)
+ bpf_obj_free_fields(meta->record, p);
+ bpf_mem_free(&bpf_global_ma, p);
+}
+
__diag_pop();
BTF_SET8_START(generic_btf_ids)
@@ -1777,6 +1787,7 @@ BTF_SET8_START(generic_btf_ids)
BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
#endif
BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
BTF_SET8_END(generic_btf_ids)
static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 804f3bca6c08..1fbb0b51c429 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7879,6 +7879,10 @@ struct bpf_kfunc_call_arg_meta {
u64 value;
bool found;
} arg_constant;
+ struct {
+ struct btf *btf;
+ u32 btf_id;
+ } arg_obj_drop;
};
static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7957,6 +7961,11 @@ static bool is_kfunc_arg_ignore(const struct btf *btf, const struct btf_param *a
return __kfunc_param_match_suffix(btf, arg, "__ign");
}
+static bool is_kfunc_arg_alloc_obj(const struct btf *btf, const struct btf_param *arg)
+{
+ return __kfunc_param_match_suffix(btf, arg, "__alloc");
+}
+
static bool is_kfunc_arg_scalar_with_name(const struct btf *btf,
const struct btf_param *arg,
const char *name)
@@ -8051,6 +8060,7 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
enum kfunc_ptr_arg_type {
KF_ARG_PTR_TO_CTX,
+ KF_ARG_PTR_TO_ALLOC_BTF_ID, /* Allocated object */
KF_ARG_PTR_TO_KPTR, /* PTR_TO_KPTR but type specific */
KF_ARG_PTR_TO_DYNPTR,
KF_ARG_PTR_TO_BTF_ID, /* Also covers reg2btf_ids conversions */
@@ -8058,6 +8068,20 @@ enum kfunc_ptr_arg_type {
KF_ARG_PTR_TO_MEM_SIZE, /* Size derived from next argument, skip it */
};
+enum special_kfunc_type {
+ KF_bpf_obj_new_impl,
+ KF_bpf_obj_drop_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+
static enum kfunc_ptr_arg_type
get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
struct bpf_kfunc_call_arg_meta *meta,
@@ -8078,6 +8102,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
return KF_ARG_PTR_TO_CTX;
+ if (is_kfunc_arg_alloc_obj(meta->btf, &args[argno]))
+ return KF_ARG_PTR_TO_ALLOC_BTF_ID;
+
if (is_kfunc_arg_kptr_get(meta, argno)) {
if (!btf_type_is_ptr(ref_t)) {
verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
@@ -8294,6 +8321,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return kf_arg_type;
switch (kf_arg_type) {
+ case KF_ARG_PTR_TO_ALLOC_BTF_ID:
case KF_ARG_PTR_TO_BTF_ID:
if (!is_kfunc_trusted_args(meta))
break;
@@ -8330,6 +8358,21 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return -EINVAL;
}
break;
+ case KF_ARG_PTR_TO_ALLOC_BTF_ID:
+ if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+ verbose(env, "arg#%d expected pointer to allocated object\n", i);
+ return -EINVAL;
+ }
+ if (!reg->ref_obj_id) {
+ verbose(env, "allocated object must be referenced\n");
+ return -EINVAL;
+ }
+ if (meta->btf == btf_vmlinux &&
+ meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ meta->arg_obj_drop.btf = reg->btf;
+ meta->arg_obj_drop.btf_id = reg->btf_id;
+ }
+ break;
case KF_ARG_PTR_TO_KPTR:
if (reg->type != PTR_TO_MAP_VALUE) {
verbose(env, "arg#0 expected pointer to map value\n");
@@ -8400,17 +8443,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return 0;
}
-enum special_kfunc_type {
- KF_bpf_obj_new_impl,
-};
-
-BTF_SET_START(special_kfunc_set)
-BTF_ID(func, bpf_obj_new_impl)
-BTF_SET_END(special_kfunc_set)
-
-BTF_ID_LIST(special_kfunc_list)
-BTF_ID(func, bpf_obj_new_impl)
-
static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx_p)
{
@@ -8532,6 +8564,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
env->insn_aux_data[insn_idx].kptr_struct_meta =
btf_find_struct_meta(ret_btf, ret_btf_id);
+ } else if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ env->insn_aux_data[insn_idx].kptr_struct_meta =
+ btf_find_struct_meta(meta.arg_obj_drop.btf,
+ meta.arg_obj_drop.btf_id);
} else {
verbose(env, "kernel function %s unhandled dynamic return type\n",
meta.func_name);
@@ -14768,6 +14804,14 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
insn_buf[2] = addr[1];
insn_buf[3] = *insn;
*cnt = 4;
+ } else if (desc->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+ struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+
+ insn_buf[0] = addr[0];
+ insn_buf[1] = addr[1];
+ insn_buf[2] = *insn;
+ *cnt = 3;
}
return 0;
}