Commit e924e80e authored by Aditi Ghag's avatar Aditi Ghag Committed by Martin KaFai Lau
Browse files

bpf: Add kfunc filter function to 'struct btf_kfunc_id_set' 



This commit adds the ability to filter kfuncs to certain BPF program
types. This is required to limit bpf_sock_destroy kfunc implemented in
follow-up commits to programs with attach type 'BPF_TRACE_ITER'.

The commit adds a callback filter to 'struct btf_kfunc_id_set'.  The
filter has access to the `bpf_prog` construct including its properties
such as `expected_attached_type`.

Signed-off-by: default avatarAditi Ghag <aditi.ghag@isovalent.com>
Link: https://lore.kernel.org/r/20230519225157.760788-7-aditi.ghag@isovalent.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent c96dac8d

include/linux/btf.h

+11 −7
Original line number Diff line number Diff line
@@ -98,10 +98,14 @@ struct btf_type; 
union bpf_attr;

struct btf_show;

struct btf_id_set;

struct bpf_prog;



typedef int (*btf_kfunc_filter_t)(const struct bpf_prog *prog, u32 kfunc_id);



struct btf_kfunc_id_set {

	struct module *owner;

	struct btf_id_set8 *set;

	btf_kfunc_filter_t filter;

};



struct btf_id_dtor_kfunc {
@@ -479,7 +483,6 @@ static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id) 
	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);

}



struct bpf_prog;

struct bpf_verifier_log;



#ifdef CONFIG_BPF_SYSCALL
@@ -487,10 +490,10 @@ const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id); 
const char *btf_name_by_offset(const struct btf *btf, u32 offset);

struct btf *btf_parse_vmlinux(void);

struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog);

u32 *btf_kfunc_id_set_contains(const struct btf *btf,

			       enum bpf_prog_type prog_type,

			       u32 kfunc_btf_id);

u32 *btf_kfunc_is_modify_return(const struct btf *btf, u32 kfunc_btf_id);

u32 *btf_kfunc_id_set_contains(const struct btf *btf, u32 kfunc_btf_id,

			       const struct bpf_prog *prog);

u32 *btf_kfunc_is_modify_return(const struct btf *btf, u32 kfunc_btf_id,

				const struct bpf_prog *prog);

int register_btf_kfunc_id_set(enum bpf_prog_type prog_type,

			      const struct btf_kfunc_id_set *s);

int register_btf_fmodret_id_set(const struct btf_kfunc_id_set *kset);
@@ -517,8 +520,9 @@ static inline const char *btf_name_by_offset(const struct btf *btf, 
	return NULL;

}

static inline u32 *btf_kfunc_id_set_contains(const struct btf *btf,

					     enum bpf_prog_type prog_type,

					     u32 kfunc_btf_id)

					     u32 kfunc_btf_id,

					     struct bpf_prog *prog)



{

	return NULL;

}

kernel/bpf/btf.c

+54 −11
Original line number Diff line number Diff line
@@ -222,10 +222,17 @@ enum btf_kfunc_hook { 
enum {

	BTF_KFUNC_SET_MAX_CNT = 256,

	BTF_DTOR_KFUNC_MAX_CNT = 256,

	BTF_KFUNC_FILTER_MAX_CNT = 16,

};



struct btf_kfunc_hook_filter {

	btf_kfunc_filter_t filters[BTF_KFUNC_FILTER_MAX_CNT];

	u32 nr_filters;

};



struct btf_kfunc_set_tab {

	struct btf_id_set8 *sets[BTF_KFUNC_HOOK_MAX];

	struct btf_kfunc_hook_filter hook_filters[BTF_KFUNC_HOOK_MAX];

};



struct btf_id_dtor_kfunc_tab {
@@ -7669,9 +7676,12 @@ static int btf_check_kfunc_protos(struct btf *btf, u32 func_id, u32 func_flags) 
/* Kernel Function (kfunc) BTF ID set registration API */



static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook,

				  struct btf_id_set8 *add_set)

				  const struct btf_kfunc_id_set *kset)

{

	struct btf_kfunc_hook_filter *hook_filter;

	struct btf_id_set8 *add_set = kset->set;

	bool vmlinux_set = !btf_is_module(btf);

	bool add_filter = !!kset->filter;

	struct btf_kfunc_set_tab *tab;

	struct btf_id_set8 *set;

	u32 set_cnt;
@@ -7686,6 +7696,24 @@ static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook, 
		return 0;



	tab = btf->kfunc_set_tab;



	if (tab && add_filter) {

		u32 i;



		hook_filter = &tab->hook_filters[hook];

		for (i = 0; i < hook_filter->nr_filters; i++) {

			if (hook_filter->filters[i] == kset->filter) {

				add_filter = false;

				break;

			}

		}



		if (add_filter && hook_filter->nr_filters == BTF_KFUNC_FILTER_MAX_CNT) {

			ret = -E2BIG;

			goto end;

		}

	}



	if (!tab) {

		tab = kzalloc(sizeof(*tab), GFP_KERNEL | __GFP_NOWARN);

		if (!tab)
@@ -7708,7 +7736,7 @@ static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook, 
	 */

	if (!vmlinux_set) {

		tab->sets[hook] = add_set;

		return 0;

		goto do_add_filter;

	}



	/* In case of vmlinux sets, there may be more than one set being
@@ -7750,6 +7778,11 @@ static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook, 


	sort(set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func, NULL);



do_add_filter:

	if (add_filter) {

		hook_filter = &tab->hook_filters[hook];

		hook_filter->filters[hook_filter->nr_filters++] = kset->filter;

	}

	return 0;

end:

	btf_free_kfunc_set_tab(btf);
@@ -7758,15 +7791,22 @@ static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook, 


static u32 *__btf_kfunc_id_set_contains(const struct btf *btf,

					enum btf_kfunc_hook hook,

					u32 kfunc_btf_id)

					u32 kfunc_btf_id,

					const struct bpf_prog *prog)

{

	struct btf_kfunc_hook_filter *hook_filter;

	struct btf_id_set8 *set;

	u32 *id;

	u32 *id, i;



	if (hook >= BTF_KFUNC_HOOK_MAX)

		return NULL;

	if (!btf->kfunc_set_tab)

		return NULL;

	hook_filter = &btf->kfunc_set_tab->hook_filters[hook];

	for (i = 0; i < hook_filter->nr_filters; i++) {

		if (hook_filter->filters[i](prog, kfunc_btf_id))

			return NULL;

	}

	set = btf->kfunc_set_tab->sets[hook];

	if (!set)

		return NULL;
@@ -7821,23 +7861,25 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type) 
 * protection for looking up a well-formed btf->kfunc_set_tab.

 */

u32 *btf_kfunc_id_set_contains(const struct btf *btf,

			       enum bpf_prog_type prog_type,

			       u32 kfunc_btf_id)

			       u32 kfunc_btf_id,

			       const struct bpf_prog *prog)

{

	enum bpf_prog_type prog_type = resolve_prog_type(prog);

	enum btf_kfunc_hook hook;

	u32 *kfunc_flags;



	kfunc_flags = __btf_kfunc_id_set_contains(btf, BTF_KFUNC_HOOK_COMMON, kfunc_btf_id);

	kfunc_flags = __btf_kfunc_id_set_contains(btf, BTF_KFUNC_HOOK_COMMON, kfunc_btf_id, prog);

	if (kfunc_flags)

		return kfunc_flags;



	hook = bpf_prog_type_to_kfunc_hook(prog_type);

	return __btf_kfunc_id_set_contains(btf, hook, kfunc_btf_id);

	return __btf_kfunc_id_set_contains(btf, hook, kfunc_btf_id, prog);

}



u32 *btf_kfunc_is_modify_return(const struct btf *btf, u32 kfunc_btf_id)

u32 *btf_kfunc_is_modify_return(const struct btf *btf, u32 kfunc_btf_id,

				const struct bpf_prog *prog)

{

	return __btf_kfunc_id_set_contains(btf, BTF_KFUNC_HOOK_FMODRET, kfunc_btf_id);

	return __btf_kfunc_id_set_contains(btf, BTF_KFUNC_HOOK_FMODRET, kfunc_btf_id, prog);

}



static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook,
@@ -7868,7 +7910,8 @@ static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook, 
			goto err_out;

	}



	ret = btf_populate_kfunc_set(btf, hook, kset->set);

	ret = btf_populate_kfunc_set(btf, hook, kset);



err_out:

	btf_put(btf);

	return ret;

kernel/bpf/verifier.c

+4 −3
Original line number Diff line number Diff line
@@ -10939,7 +10939,7 @@ static int fetch_kfunc_meta(struct bpf_verifier_env *env, 
		*kfunc_name = func_name;

	func_proto = btf_type_by_id(desc_btf, func->type);









	kfunc_flags = btf_kfunc_id_set_contains(desc_btf, resolve_prog_type(env->prog), func_id);









	kfunc_flags = btf_kfunc_id_set_contains(desc_btf, func_id, env->prog);









	if (!kfunc_flags) {









		return -EACCES;









	}








@@ -19010,7 +19010,8 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,







				 * in the fmodret id set with the KF_SLEEPABLE flag.









				 */









				else {









					u32 *flags = btf_kfunc_is_modify_return(btf, btf_id);









					u32 *flags = btf_kfunc_is_modify_return(btf, btf_id,









										prog);

















					if (flags && (*flags & KF_SLEEPABLE))









						ret = 0;








@@ -19038,7 +19039,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,







				return -EINVAL;









			}









			ret = -EINVAL;









			if (btf_kfunc_is_modify_return(btf, btf_id) ||









			if (btf_kfunc_is_modify_return(btf, btf_id, prog) ||









			    !check_attach_modify_return(addr, tname))









				ret = 0;









			if (ret) {