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

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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: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240808232230.2848712-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-08-08 16:22:29 -07:00 committed by Alexei Starovoitov
parent 496ddd19a0
commit baebe9aaba
1 changed files with 24 additions and 11 deletions
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35
kernel/bpf/verifier.c
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@ -7970,12 +7970,17 @@ static bool is_iter_destroy_kfunc(struct bpf_kfunc_call_arg_meta *meta)
return meta->kfunc_flags & KF_ITER_DESTROY; 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 /* btf_check_iter_kfuncs() guarantees that first argument of any iter
* kfunc is iter state pointer * 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, 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]; struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
const struct btf_type *t; const struct btf_type *t;
const struct btf_param *arg; int spi, err, i, nr_slots, btf_id;
int spi, err, i, nr_slots;
u32 btf_id;
/* btf_check_iter_kfuncs() ensures we don't need to validate anything here */ /* For iter_{new,next,destroy} functions, btf_check_iter_kfuncs()
arg = &btf_params(meta->func_proto)[0]; * ensures struct convention, so we wouldn't need to do any BTF
t = btf_type_skip_modifiers(meta->btf, arg->type, NULL); /* PTR */ * validation here. But given iter state can be passed as a parameter
t = btf_type_skip_modifiers(meta->btf, t->type, &btf_id); /* STRUCT */ * 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; nr_slots = t->size / BPF_REG_SIZE;
if (is_iter_new_kfunc(meta)) { 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) if (err)
return err; return err;
} else { } 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); err = is_iter_reg_valid_init(env, reg, meta->btf, btf_id, nr_slots);
switch (err) { switch (err) {
case 0: 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])) if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
return KF_ARG_PTR_TO_DYNPTR; 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; return KF_ARG_PTR_TO_ITER;
if (is_kfunc_arg_list_head(meta->btf, &args[argno])) if (is_kfunc_arg_list_head(meta->btf, &args[argno]))