From: Kui-Feng Lee <sinquersw@gmail.com>
To: Martin KaFai Lau <martin.lau@linux.dev>, thinker.li@gmail.com
Cc: kuifeng@meta.com, bpf@vger.kernel.org, ast@kernel.org,
song@kernel.org, kernel-team@meta.com, andrii@kernel.org
Subject: Re: [RFC bpf-next v3 05/11] bpf: hold module for bpf_struct_ops_map.
Date: Mon, 25 Sep 2023 16:42:57 -0700 [thread overview]
Message-ID: <437cd950-90ad-9cf4-8cb4-caa9538fef36@gmail.com> (raw)
In-Reply-To: <8393a1f3-b4cf-9e4c-ce76-4b09a3f1622b@linux.dev>
On 9/25/23 16:23, Martin KaFai Lau wrote:
> On 9/20/23 8:59 AM, thinker.li@gmail.com wrote:
>> From: Kui-Feng Lee <thinker.li@gmail.com>
>>
>> Ensure a module doesn't go away when a struct_ops object is still alive,
>> being a struct_ops type that is registered by the module.
>>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>> include/linux/bpf.h | 1 +
>> kernel/bpf/bpf_struct_ops.c | 6 ++++++
>> 2 files changed, 7 insertions(+)
>>
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index 0776cb584b3f..faaec20156f1 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -1627,6 +1627,7 @@ struct bpf_struct_ops {
>> int (*update)(void *kdata, void *old_kdata);
>> int (*validate)(void *kdata);
>> const struct btf *btf;
>> + struct module *owner;
>> const struct btf_type *type;
>> const struct btf_type *value_type;
>> const char *name;
>> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
>> index 7c2ef53687ef..ef8a1edec891 100644
>> --- a/kernel/bpf/bpf_struct_ops.c
>> +++ b/kernel/bpf/bpf_struct_ops.c
>> @@ -632,6 +632,8 @@ static void __bpf_struct_ops_map_free(struct
>> bpf_map *map)
>> static void bpf_struct_ops_map_free(struct bpf_map *map)
>> {
>> + struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map
>> *)map;
>> +
>> /* The struct_ops's function may switch to another struct_ops.
>> *
>> * For example, bpf_tcp_cc_x->init() may switch to
>> @@ -649,6 +651,7 @@ static void bpf_struct_ops_map_free(struct bpf_map
>> *map)
>> */
>> synchronize_rcu_mult(call_rcu, call_rcu_tasks);
>> + module_put(st_map->st_ops->owner);
>> __bpf_struct_ops_map_free(map);
>> }
>> @@ -673,6 +676,9 @@ static struct bpf_map
>> *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>> if (!st_ops)
>> return ERR_PTR(-ENOTSUPP);
>> + if (!try_module_get(st_ops->owner))
>> + return ERR_PTR(-EINVAL);
>
> The module can be gone at this point?
> I don't think try_module_get is safe. btf_try_get_module should be used
> instead.
At this point, it holds btf, but not module. Module can go away while
some one still holding a refcount to the btf.
And, you are right, I should use btf_try_get_module().
>
>> +
>> vt = st_ops->value_type;
>> if (attr->value_size != vt->size)
>> return ERR_PTR(-EINVAL);
>
next prev parent reply other threads:[~2023-09-25 23:43 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-20 15:59 [RFC bpf-next v3 00/11] Registrating struct_ops types from modules thinker.li
2023-09-20 15:59 ` [RFC bpf-next v3 01/11] bpf: refactory struct_ops type initialization to a function thinker.li
2023-09-20 15:59 ` [RFC bpf-next v3 02/11] bpf: add struct_ops_tab to btf thinker.li
2023-09-25 21:10 ` Martin KaFai Lau
2023-09-25 21:45 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 03/11] bpf: add register and unregister functions for struct_ops thinker.li
2023-09-25 23:07 ` Martin KaFai Lau
2023-09-25 23:13 ` Kui-Feng Lee
2023-09-25 23:31 ` Martin KaFai Lau
2023-09-26 0:19 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 04/11] bpf: attach a module BTF to a bpf_struct_ops thinker.li
2023-09-25 22:57 ` Martin KaFai Lau
2023-09-25 23:25 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 05/11] bpf: hold module for bpf_struct_ops_map thinker.li
2023-09-25 23:23 ` Martin KaFai Lau
2023-09-25 23:42 ` Kui-Feng Lee [this message]
2023-09-20 15:59 ` [RFC bpf-next v3 06/11] bpf: validate value_type thinker.li
2023-09-26 1:03 ` Martin KaFai Lau
2023-09-27 20:27 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 07/11] bpf, net: switch to storing struct_ops in btf thinker.li
2023-09-26 0:02 ` Martin KaFai Lau
2023-09-26 0:18 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 08/11] bpf: pass attached BTF to find correct type info of struct_ops progs thinker.li
2023-09-25 22:58 ` Andrii Nakryiko
2023-09-25 23:50 ` Kui-Feng Lee
2023-09-26 0:24 ` Martin KaFai Lau
2023-09-26 0:58 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 09/11] libbpf: Find correct module BTFs for struct_ops maps and progs thinker.li
2023-09-25 23:09 ` Andrii Nakryiko
2023-09-26 0:12 ` Kui-Feng Lee
2023-09-20 15:59 ` [RFC bpf-next v3 10/11] bpf: export btf_ctx_access to modules thinker.li
2023-09-20 15:59 ` [RFC bpf-next v3 11/11] selftests/bpf: test case for register_bpf_struct_ops() thinker.li
2023-09-26 1:19 ` Martin KaFai Lau
2023-09-26 1:33 ` [RFC bpf-next v3 00/11] Registrating struct_ops types from modules Martin KaFai Lau
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