From: Kui-Feng Lee <sinquersw@gmail.com>
To: Eduard Zingerman <eddyz87@gmail.com>,
thinker.li@gmail.com, bpf@vger.kernel.org, ast@kernel.org,
martin.lau@linux.dev, song@kernel.org, kernel-team@meta.com,
andrii@kernel.org, drosen@google.com
Cc: kuifeng@meta.com
Subject: Re: [PATCH bpf-next v6 04/10] bpf: hold module for bpf_struct_ops_map.
Date: Thu, 26 Oct 2023 21:35:25 -0700 [thread overview]
Message-ID: <a57d72c9-ca37-4eea-89b9-2271042fecdc@gmail.com> (raw)
In-Reply-To: <fe10e843372f3100419da42a047e0b8ae6967fb6.camel@gmail.com>
On 10/26/23 14:11, Eduard Zingerman wrote:
> On Sat, 2023-10-21 at 22:03 -0700, thinker.li@gmail.com wrote:
>> From: Kui-Feng Lee <thinker.li@gmail.com>
>>
>> To ensure that a module remains accessible whenever a struct_ops object of
>> a struct_ops type provided by the module is still in use.
>>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>> include/linux/bpf.h | 1 +
>> include/linux/btf.h | 2 +-
>> kernel/bpf/bpf_struct_ops.c | 70 ++++++++++++++++++++++++++++++-------
>> 3 files changed, 60 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index 4f3b67932ded..26feb8a2da4f 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -1626,6 +1626,7 @@ struct bpf_struct_ops {
>> void (*unreg)(void *kdata);
>> int (*update)(void *kdata, void *old_kdata);
>> int (*validate)(void *kdata);
>> + struct module *owner;
>> const char *name;
>> struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
>> };
>> diff --git a/include/linux/btf.h b/include/linux/btf.h
>> index 8e37f7eb02c7..6a64b372b7a0 100644
>> --- a/include/linux/btf.h
>> +++ b/include/linux/btf.h
>> @@ -575,7 +575,7 @@ struct bpf_struct_ops;
>> struct bpf_struct_ops_desc;
>>
>> struct bpf_struct_ops_desc *
>> -btf_add_struct_ops(struct bpf_struct_ops *st_ops);
>> +btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops);
>> const struct bpf_struct_ops_desc *
>> btf_get_struct_ops(struct btf *btf, u32 *ret_cnt);
>>
>> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
>> index 0bc21a39257d..413a3f8b26ba 100644
>> --- a/kernel/bpf/bpf_struct_ops.c
>> +++ b/kernel/bpf/bpf_struct_ops.c
>> @@ -388,6 +388,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
>> const struct btf_member *member;
>> const struct btf_type *t = st_ops_desc->type;
>> struct bpf_tramp_links *tlinks;
>> + struct module *mod = NULL;
>> void *udata, *kdata;
>> int prog_fd, err;
>> void *image, *image_end;
>> @@ -425,6 +426,14 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
>> goto unlock;
>> }
>>
>> + if (st_ops_desc->btf != btf_vmlinux) {
>> + mod = btf_try_get_module(st_ops_desc->btf);
>> + if (!mod) {
>> + err = -EBUSY;
>
> Nit: there is a disagreement about error code returned for
> failing btf_try_get_module() across verifier code base:
> - EINVAL is used 2 times;
> - ENXIO is used 3 times;
> - ENOTSUPP is used once.
> Are you sure EBUSY is a good choice here?
You are right. I think EINVAL is better or this case.
>
>> + goto unlock;
>> + }
>> + }
>> +
>> memcpy(uvalue, value, map->value_size);
>>
>> udata = &uvalue->data;
>> @@ -552,6 +561,10 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
>> * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
>> */
>> smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
>> + /* Hold the owner module until the struct_ops is
>> + * unregistered
>> + */
>> + mod = NULL;
>> goto unlock;
>> }
>>
>> @@ -568,6 +581,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
>> memset(uvalue, 0, map->value_size);
>> memset(kvalue, 0, map->value_size);
>> unlock:
>> + module_put(mod);
>> kfree(tlinks);
>> mutex_unlock(&st_map->lock);
>> return err;
>> @@ -588,6 +602,7 @@ static long bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
>> switch (prev_state) {
>> case BPF_STRUCT_OPS_STATE_INUSE:
>> st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data);
>> + module_put(st_map->st_ops_desc->st_ops->owner);
>> bpf_map_put(map);
>> return 0;
>> case BPF_STRUCT_OPS_STATE_TOBEFREE:
>> @@ -674,6 +689,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>> size_t st_map_size;
>> struct bpf_struct_ops_map *st_map;
>> const struct btf_type *t, *vt;
>> + struct module *mod = NULL;
>> struct bpf_map *map;
>> int ret;
>>
>> @@ -681,9 +697,17 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>> if (!st_ops_desc)
>> return ERR_PTR(-ENOTSUPP);
>>
>> + if (st_ops_desc->btf != btf_vmlinux) {
>> + mod = btf_try_get_module(st_ops_desc->btf);
>> + if (!mod)
>> + return ERR_PTR(-EINVAL);
>> + }
>> +
>> vt = st_ops_desc->value_type;
>> - if (attr->value_size != vt->size)
>> - return ERR_PTR(-EINVAL);
>> + if (attr->value_size != vt->size) {
>> + ret = -EINVAL;
>> + goto errout;
>> + }
>>
>> t = st_ops_desc->type;
>>
>> @@ -694,17 +718,17 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>> (vt->size - sizeof(struct bpf_struct_ops_value));
>>
>> st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
>> - if (!st_map)
>> - return ERR_PTR(-ENOMEM);
>> + if (!st_map) {
>> + ret = -ENOMEM;
>> + goto errout;
>> + }
>>
>> st_map->st_ops_desc = st_ops_desc;
>> map = &st_map->map;
>>
>> ret = bpf_jit_charge_modmem(PAGE_SIZE);
>> - if (ret) {
>> - __bpf_struct_ops_map_free(map);
>> - return ERR_PTR(ret);
>> - }
>> + if (ret)
>> + goto errout_free;
>>
>> st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
>> if (!st_map->image) {
>> @@ -713,23 +737,32 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>> * here.
>> */
>> bpf_jit_uncharge_modmem(PAGE_SIZE);
>> - __bpf_struct_ops_map_free(map);
>> - return ERR_PTR(-ENOMEM);
>> + ret = -ENOMEM;
>> + goto errout_free;
>> }
>> st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
>> st_map->links =
>> bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_links *),
>> NUMA_NO_NODE);
>> if (!st_map->uvalue || !st_map->links) {
>> - __bpf_struct_ops_map_free(map);
>> - return ERR_PTR(-ENOMEM);
>> + ret = -ENOMEM;
>> + goto errout_free;
>> }
>>
>> mutex_init(&st_map->lock);
>> set_vm_flush_reset_perms(st_map->image);
>> bpf_map_init_from_attr(map, attr);
>>
>> + module_put(mod);
>> +
>> return map;
>> +
>> +errout_free:
>> + __bpf_struct_ops_map_free(map);
>> + btf = NULL; /* has been released */
>> +errout:
>> + module_put(mod);
>> + return ERR_PTR(ret);
>> }
>>
>> static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
>> @@ -811,6 +844,7 @@ static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
>> * bpf_struct_ops_link_create() fails to register.
>> */
>> st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data);
>> + module_put(st_map->st_ops_desc->st_ops->owner);
>> bpf_map_put(&st_map->map);
>> }
>> kfree(st_link);
>> @@ -857,6 +891,10 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map
>> if (!bpf_struct_ops_valid_to_reg(new_map))
>> return -EINVAL;
>>
>> + /* The old map is holding the refcount for the owner module. The
>> + * ownership of the owner module refcount is going to be
>> + * transferred from the old map to the new map.
>> + */
>> if (!st_map->st_ops_desc->st_ops->update)
>> return -EOPNOTSUPP;
>>
>> @@ -902,6 +940,7 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
>> struct bpf_link_primer link_primer;
>> struct bpf_struct_ops_map *st_map;
>> struct bpf_map *map;
>> + struct btf *btf;
>> int err;
>>
>> map = bpf_map_get(attr->link_create.map_fd);
>> @@ -926,8 +965,15 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
>> if (err)
>> goto err_out;
>>
>> + /* Hold the owner module until the struct_ops is unregistered. */
>> + btf = st_map->st_ops_desc->btf;
>> + if (btf != btf_vmlinux && !btf_try_get_module(btf)) {
>> + err = -EINVAL;
>> + goto err_out;
>> + }
>> err = st_map->st_ops_desc->st_ops->reg(st_map->kvalue.data);
>> if (err) {
>> + module_put(st_map->st_ops_desc->st_ops->owner);
>> bpf_link_cleanup(&link_primer);
>> link = NULL;
>> goto err_out;
>
next prev parent reply other threads:[~2023-10-27 4:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-22 5:03 [PATCH bpf-next v6 00/10] Registrating struct_ops types from modules thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 01/10] bpf: refactory struct_ops type initialization to a function thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 02/10] bpf, net: introduce bpf_struct_ops_desc thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 03/10] bpf: add struct_ops_tab to btf thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 04/10] bpf: hold module for bpf_struct_ops_map thinker.li
2023-10-26 21:11 ` Eduard Zingerman
2023-10-27 4:35 ` Kui-Feng Lee [this message]
2023-10-22 5:03 ` [PATCH bpf-next v6 05/10] bpf: validate value_type thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 06/10] bpf: pass attached BTF to the bpf_struct_ops subsystem thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 07/10] bpf, net: switch to dynamic registration thinker.li
2023-10-22 6:46 ` kernel test robot
2023-10-26 21:02 ` Eduard Zingerman
2023-10-27 4:39 ` Kui-Feng Lee
2023-10-27 21:32 ` Kui-Feng Lee
2023-10-27 22:02 ` Eduard Zingerman
2023-10-22 5:03 ` [PATCH bpf-next v6 08/10] libbpf: Find correct module BTFs for struct_ops maps and progs thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 09/10] bpf: export btf_ctx_access to modules thinker.li
2023-10-22 5:03 ` [PATCH bpf-next v6 10/10] selftests/bpf: test case for register_bpf_struct_ops() thinker.li
2023-10-22 7:08 ` kernel test robot
2023-10-26 20:31 ` Eduard Zingerman
2023-10-27 4:55 ` Kui-Feng Lee
2023-10-27 7:09 ` Kui-Feng Lee
2023-10-27 14:13 ` Eduard Zingerman
2023-10-29 2:34 ` Kui-Feng Lee
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