[v2,bpf-next,1/2] bpf: Check percpu map value size first

Commit Message

Tao Chen Sept. 9, 2024, 7:13 a.m. UTC

Percpu map is often used, but the map value size limit often ignored,
like issue: https://github.com/iovisor/bcc/issues/2519. Actually,
percpu map value size is bound by PCPU_MIN_UNIT_SIZE, so we
can check the value size whether it exceeds PCPU_MIN_UNIT_SIZE first,
like percpu map of local_storage. Maybe the error message seems clearer
compared with "cannot allocate memory".

Signed-off-by: Tao Chen <[e-mail]>
Signed-off-by: jinke han <[e-mail]>
---
 kernel/bpf/arraymap.c | 3 +++
 kernel/bpf/hashtab.c  | 3 +++
 2 files changed, 6 insertions(+)

Comments

Andrii Nakryiko Sept. 9, 2024, 8:17 p.m. UTC | #1

On Mon, Sep 9, 2024 at 12:14 AM Tao Chen <[e-mail]> wrote:
>
> Percpu map is often used, but the map value size limit often ignored,
> like issue: https://github.com/iovisor/bcc/issues/2519. Actually,
> percpu map value size is bound by PCPU_MIN_UNIT_SIZE, so we
> can check the value size whether it exceeds PCPU_MIN_UNIT_SIZE first,
> like percpu map of local_storage. Maybe the error message seems clearer
> compared with "cannot allocate memory".
>
> Signed-off-by: Tao Chen <[e-mail]>
> Signed-off-by: jinke han <[e-mail]>

names in SOB should be capitalized

the check is useful, so:

Acked-by: Andrii Nakryiko <[e-mail]>

> ---
>  kernel/bpf/arraymap.c | 3 +++
>  kernel/bpf/hashtab.c  | 3 +++
>  2 files changed, 6 insertions(+)
>
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index a43e62e2a8bb..79660e3fca4c 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -73,6 +73,9 @@ int array_map_alloc_check(union bpf_attr *attr)
>         /* avoid overflow on round_up(map->value_size) */
>         if (attr->value_size > INT_MAX)
>                 return -E2BIG;
> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
> +               return -E2BIG;
>
>         return 0;
>  }
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 45c7195b65ba..b14b87463ee0 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -462,6 +462,9 @@ static int htab_map_alloc_check(union bpf_attr *attr)
>                  * kmalloc-able later in htab_map_update_elem()
>                  */
>                 return -E2BIG;
> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
> +               return -E2BIG;
>
>         return 0;
>  }
> --
> 2.25.1
>

Tao Chen Sept. 10, 2024, 2:35 a.m. UTC | #2

在 2024/9/10 04:17, Andrii Nakryiko 写道:
> On Mon, Sep 9, 2024 at 12:14 AM Tao Chen <[e-mail]> wrote:
>>
>> Percpu map is often used, but the map value size limit often ignored,
>> like issue: https://github.com/iovisor/bcc/issues/2519. Actually,
>> percpu map value size is bound by PCPU_MIN_UNIT_SIZE, so we
>> can check the value size whether it exceeds PCPU_MIN_UNIT_SIZE first,
>> like percpu map of local_storage. Maybe the error message seems clearer
>> compared with "cannot allocate memory".
>>
>> Signed-off-by: Tao Chen <[e-mail]>
>> Signed-off-by: jinke han <[e-mail]>
> 
> names in SOB should be capitalized

Hi Andrii，thank you for your attention, i will change it.

> 
> the check is useful, so:
> 
> Acked-by: Andrii Nakryiko <[e-mail]>
> 
>> ---
>>   kernel/bpf/arraymap.c | 3 +++
>>   kernel/bpf/hashtab.c  | 3 +++
>>   2 files changed, 6 insertions(+)
>>
>> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
>> index a43e62e2a8bb..79660e3fca4c 100644
>> --- a/kernel/bpf/arraymap.c
>> +++ b/kernel/bpf/arraymap.c
>> @@ -73,6 +73,9 @@ int array_map_alloc_check(union bpf_attr *attr)
>>          /* avoid overflow on round_up(map->value_size) */
>>          if (attr->value_size > INT_MAX)
>>                  return -E2BIG;
>> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
>> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
>> +               return -E2BIG;
>>
>>          return 0;
>>   }
>> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
>> index 45c7195b65ba..b14b87463ee0 100644
>> --- a/kernel/bpf/hashtab.c
>> +++ b/kernel/bpf/hashtab.c
>> @@ -462,6 +462,9 @@ static int htab_map_alloc_check(union bpf_attr *attr)
>>                   * kmalloc-able later in htab_map_update_elem()
>>                   */
>>                  return -E2BIG;
>> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
>> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
>> +               return -E2BIG;
>>
>>          return 0;
>>   }
>> --
>> 2.25.1
>>

Patch

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index a43e62e2a8bb..79660e3fca4c 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -73,6 +73,9 @@  int array_map_alloc_check(union bpf_attr *attr)
 	/* avoid overflow on round_up(map->value_size) */
 	if (attr->value_size > INT_MAX)
 		return -E2BIG;
+	/* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
+	if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
+		return -E2BIG;
 
 	return 0;
 }
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 45c7195b65ba..b14b87463ee0 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -462,6 +462,9 @@  static int htab_map_alloc_check(union bpf_attr *attr)
 		 * kmalloc-able later in htab_map_update_elem()
 		 */
 		return -E2BIG;
+	/* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
+	if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
+		return -E2BIG;
 
 	return 0;
 }