Commit baebe9aa authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

bpf: allow passing struct bpf_iter_<type> as kfunc arguments 



There are potentially useful cases where a specific iterator type might
need to be passed into some kfunc. So, in addition to existing
bpf_iter_<type>_{new,next,destroy}() kfuncs, allow to pass iterator
pointer to any kfunc.

We employ "__iter" naming suffix for arguments that are meant to accept
iterators. We also enforce that they accept PTR -> STRUCT btf_iter_<type>
type chain and point to a valid initialized on-the-stack iterator state.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240808232230.2848712-3-andrii@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 496ddd19

kernel/bpf/verifier.c

+24 −11
Original line number Diff line number Diff line
@@ -7970,12 +7970,17 @@ static bool is_iter_destroy_kfunc(struct bpf_kfunc_call_arg_meta *meta) 
	return meta->kfunc_flags & KF_ITER_DESTROY;

}









static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg)









static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx,









			      const struct btf_param *arg)









{









	/* btf_check_iter_kfuncs() guarantees that first argument of any iter









	 * kfunc is iter state pointer









	 */









	return arg == 0 && is_iter_kfunc(meta);









	if (is_iter_kfunc(meta))









		return arg_idx == 0;

















	/* iter passed as an argument to a generic kfunc */









	return btf_param_match_suffix(meta->btf, arg, "__iter");









}

















static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_idx,








@@ -7983,14 +7988,20 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id







{









	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];









	const struct btf_type *t;









	const struct btf_param *arg;









	int spi, err, i, nr_slots;









	u32 btf_id;









	int spi, err, i, nr_slots, btf_id;

















	/* btf_check_iter_kfuncs() ensures we don't need to validate anything here */









	arg = &btf_params(meta->func_proto)[0];









	t = btf_type_skip_modifiers(meta->btf, arg->type, NULL);	/* PTR */









	t = btf_type_skip_modifiers(meta->btf, t->type, &btf_id);	/* STRUCT */









	/* For iter_{new,next,destroy} functions, btf_check_iter_kfuncs()









	 * ensures struct convention, so we wouldn't need to do any BTF









	 * validation here. But given iter state can be passed as a parameter









	 * to any kfunc, if arg has "__iter" suffix, we need to be a bit more









	 * conservative here.









	 */









	btf_id = btf_check_iter_arg(meta->btf, meta->func_proto, regno - 1);









	if (btf_id < 0) {









		verbose(env, "expected valid iter pointer as arg #%d\n", regno);









		return -EINVAL;









	}









	t = btf_type_by_id(meta->btf, btf_id);









	nr_slots = t->size / BPF_REG_SIZE;

















	if (is_iter_new_kfunc(meta)) {








@@ -8012,7 +8023,9 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id







		if (err)









			return err;









	} else {









		/* iter_next() or iter_destroy() expect initialized iter state*/









		/* iter_next() or iter_destroy(), as well as any kfunc









		 * accepting iter argument, expect initialized iter state









		 */









		err = is_iter_reg_valid_init(env, reg, meta->btf, btf_id, nr_slots);









		switch (err) {









		case 0:








@@ -11382,7 +11395,7 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,







	if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))









		return KF_ARG_PTR_TO_DYNPTR;

















	if (is_kfunc_arg_iter(meta, argno))









	if (is_kfunc_arg_iter(meta, argno, &args[argno]))









		return KF_ARG_PTR_TO_ITER;

















	if (is_kfunc_arg_list_head(meta->btf, &args[argno]))