ceph: Annotate struct ceph_monmap with __counted_by

  Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: ceph-devel@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/ceph/mon_client.h | 2 +-
 net/ceph/mon_client.c           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
  

On 9/16/23 04:15, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Ilya Dryomov <idryomov@gmail.com>
> Cc: Xiubo Li <xiubli@redhat.com>
> Cc: Jeff Layton <jlayton@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: ceph-devel@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>   include/linux/ceph/mon_client.h | 2 +-
>   net/ceph/mon_client.c           | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
> index b658961156a0..7a9a40163c0f 100644
> --- a/include/linux/ceph/mon_client.h
> +++ b/include/linux/ceph/mon_client.h
> @@ -19,7 +19,7 @@ struct ceph_monmap {
>   	struct ceph_fsid fsid;
>   	u32 epoch;
>   	u32 num_mon;
> -	struct ceph_entity_inst mon_inst[];
> +	struct ceph_entity_inst mon_inst[] __counted_by(num_mon);
>   };
>   
>   struct ceph_mon_client;
> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
> index faabad6603db..f263f7e91a21 100644
> --- a/net/ceph/mon_client.c
> +++ b/net/ceph/mon_client.c
> @@ -1136,6 +1136,7 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>   			       GFP_KERNEL);
>   	if (!monc->monmap)
>   		return -ENOMEM;
> +	monc->monmap->num_mon = num_mon;
>   
>   	for (i = 0; i < num_mon; i++) {
>   		struct ceph_entity_inst *inst = &monc->monmap->mon_inst[i];
> @@ -1147,7 +1148,6 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>   		inst->name.type = CEPH_ENTITY_TYPE_MON;
>   		inst->name.num = cpu_to_le64(i);
>   	}
> -	monc->monmap->num_mon = num_mon;

BTW, is this change related ?

>   	return 0;
>   }
>   

Else LGTM.

Reviewed-by: Xiubo Li <xiubli@redhat.com>

Thanks!

- Xiubo
  

On September 17, 2023 5:25:10 PM PDT, Xiubo Li <xiubli@redhat.com> wrote:
>
>On 9/16/23 04:15, Kees Cook wrote:
> > [...]
>> Additionally, since the element count member must be set before accessing
>> the annotated flexible array member, move its initialization earlier.
>> 
>> [...]
>> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
>> index faabad6603db..f263f7e91a21 100644
>> --- a/net/ceph/mon_client.c
>> +++ b/net/ceph/mon_client.c
>> @@ -1136,6 +1136,7 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>>   			       GFP_KERNEL);
>>   	if (!monc->monmap)
>>   		return -ENOMEM;
>> +	monc->monmap->num_mon = num_mon;
>>     	for (i = 0; i < num_mon; i++) {
>>   		struct ceph_entity_inst *inst = &monc->monmap->mon_inst[i];
>> @@ -1147,7 +1148,6 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>>   		inst->name.type = CEPH_ENTITY_TYPE_MON;
>>   		inst->name.num = cpu_to_le64(i);
>>   	}
>> -	monc->monmap->num_mon = num_mon;
>
>BTW, is this change related ?

Yes, this is needed so that the __counted_by size is set before accessing the flexible array.

>
>>   	return 0;
>>   }
>>   
>
>Else LGTM.
>
>Reviewed-by: Xiubo Li <xiubli@redhat.com>

Thanks!
  

On 9/17/23 18:25, Xiubo Li wrote:
> 
> On 9/16/23 04:15, Kees Cook wrote:
>> Prepare for the coming implementation by GCC and Clang of the __counted_by
>> attribute. Flexible array members annotated with __counted_by can have
>> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
>> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
>> functions).
>>
>> As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
>> Additionally, since the element count member must be set before accessing
>> the annotated flexible array member, move its initialization earlier.
>>
>> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>>
>> Cc: Ilya Dryomov <idryomov@gmail.com>
>> Cc: Xiubo Li <xiubli@redhat.com>
>> Cc: Jeff Layton <jlayton@kernel.org>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: Eric Dumazet <edumazet@google.com>
>> Cc: Jakub Kicinski <kuba@kernel.org>
>> Cc: Paolo Abeni <pabeni@redhat.com>
>> Cc: ceph-devel@vger.kernel.org
>> Cc: netdev@vger.kernel.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>   include/linux/ceph/mon_client.h | 2 +-
>>   net/ceph/mon_client.c           | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
>> index b658961156a0..7a9a40163c0f 100644
>> --- a/include/linux/ceph/mon_client.h
>> +++ b/include/linux/ceph/mon_client.h
>> @@ -19,7 +19,7 @@ struct ceph_monmap {
>>       struct ceph_fsid fsid;
>>       u32 epoch;
>>       u32 num_mon;
>> -    struct ceph_entity_inst mon_inst[];
>> +    struct ceph_entity_inst mon_inst[] __counted_by(num_mon);
>>   };
>>   struct ceph_mon_client;
>> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
>> index faabad6603db..f263f7e91a21 100644
>> --- a/net/ceph/mon_client.c
>> +++ b/net/ceph/mon_client.c
>> @@ -1136,6 +1136,7 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>>                      GFP_KERNEL);
>>       if (!monc->monmap)
>>           return -ENOMEM;
>> +    monc->monmap->num_mon = num_mon;
>>       for (i = 0; i < num_mon; i++) {
>>           struct ceph_entity_inst *inst = &monc->monmap->mon_inst[i];
>> @@ -1147,7 +1148,6 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
>>           inst->name.type = CEPH_ENTITY_TYPE_MON;
>>           inst->name.num = cpu_to_le64(i);
>>       }
>> -    monc->monmap->num_mon = num_mon;
> 
> BTW, is this change related ?

Yes, it is, and it's described in the changelog text.

`num_mon` must be updated before the first access to flex-array `mon_inst`.
Otherwise the compiler cannot properly instrument the code to catch any
out-of-bounds access to `mon_inst`.

--
Gustavo

> 
>>       return 0;
>>   }
> 
> Else LGTM.
> 
> Reviewed-by: Xiubo Li <xiubli@redhat.com>
> 
> Thanks!
> 
> - Xiubo
> 
>
  

On 9/18/23 10:04, Gustavo A. R. Silva wrote:
>
>
> On 9/17/23 18:25, Xiubo Li wrote:
>>
>> On 9/16/23 04:15, Kees Cook wrote:
>>> Prepare for the coming implementation by GCC and Clang of the 
>>> __counted_by
>>> attribute. Flexible array members annotated with __counted_by can have
>>> their accesses bounds-checked at run-time checking via 
>>> CONFIG_UBSAN_BOUNDS
>>> (for array indexing) and CONFIG_FORTIFY_SOURCE (for 
>>> strcpy/memcpy-family
>>> functions).
>>>
>>> As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
>>> Additionally, since the element count member must be set before 
>>> accessing
>>> the annotated flexible array member, move its initialization earlier.
>>>
>>> [1] 
>>> https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>>>
>>> Cc: Ilya Dryomov <idryomov@gmail.com>
>>> Cc: Xiubo Li <xiubli@redhat.com>
>>> Cc: Jeff Layton <jlayton@kernel.org>
>>> Cc: "David S. Miller" <davem@davemloft.net>
>>> Cc: Eric Dumazet <edumazet@google.com>
>>> Cc: Jakub Kicinski <kuba@kernel.org>
>>> Cc: Paolo Abeni <pabeni@redhat.com>
>>> Cc: ceph-devel@vger.kernel.org
>>> Cc: netdev@vger.kernel.org
>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>> ---
>>>   include/linux/ceph/mon_client.h | 2 +-
>>>   net/ceph/mon_client.c           | 2 +-
>>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/ceph/mon_client.h 
>>> b/include/linux/ceph/mon_client.h
>>> index b658961156a0..7a9a40163c0f 100644
>>> --- a/include/linux/ceph/mon_client.h
>>> +++ b/include/linux/ceph/mon_client.h
>>> @@ -19,7 +19,7 @@ struct ceph_monmap {
>>>       struct ceph_fsid fsid;
>>>       u32 epoch;
>>>       u32 num_mon;
>>> -    struct ceph_entity_inst mon_inst[];
>>> +    struct ceph_entity_inst mon_inst[] __counted_by(num_mon);
>>>   };
>>>   struct ceph_mon_client;
>>> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
>>> index faabad6603db..f263f7e91a21 100644
>>> --- a/net/ceph/mon_client.c
>>> +++ b/net/ceph/mon_client.c
>>> @@ -1136,6 +1136,7 @@ static int build_initial_monmap(struct 
>>> ceph_mon_client *monc)
>>>                      GFP_KERNEL);
>>>       if (!monc->monmap)
>>>           return -ENOMEM;
>>> +    monc->monmap->num_mon = num_mon;
>>>       for (i = 0; i < num_mon; i++) {
>>>           struct ceph_entity_inst *inst = &monc->monmap->mon_inst[i];
>>> @@ -1147,7 +1148,6 @@ static int build_initial_monmap(struct 
>>> ceph_mon_client *monc)
>>>           inst->name.type = CEPH_ENTITY_TYPE_MON;
>>>           inst->name.num = cpu_to_le64(i);
>>>       }
>>> -    monc->monmap->num_mon = num_mon;
>>
>> BTW, is this change related ?
>
> Yes, it is, and it's described in the changelog text.
>
> `num_mon` must be updated before the first access to flex-array 
> `mon_inst`.
> Otherwise the compiler cannot properly instrument the code to catch any
> out-of-bounds access to `mon_inst`.
>
Okay, got it.

Thanks

- Xiubo


> -- 
> Gustavo
>
>>
>>>       return 0;
>>>   }
>>
>> Else LGTM.
>>
>> Reviewed-by: Xiubo Li <xiubli@redhat.com>
>>
>> Thanks!
>>
>> - Xiubo
>>
>>
>
  

Hello:

This patch was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri, 15 Sep 2023 13:15:10 -0700 you wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [...]

Here is the summary with links:
  - ceph: Annotate struct ceph_monmap with __counted_by
    https://git.kernel.org/netdev/net-next/c/1cb6422ecac8

You are awesome, thank you!