linux-hardening - Re: [PATCH 1/2][next] vfio/ccw: Replace one-element array with flexible-array member

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Date:   Tue, 23 May 2023 19:47:03 +0200
From:   Marion & Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Eric Farman <farman@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/2][next] vfio/ccw: Replace one-element array with
 flexible-array member



Le 23/05/2023 à 19:45, Christophe JAILLET a écrit :
> Le 23/05/2023 à 03:35, Gustavo A. R. Silva a écrit :
>> One-element arrays are deprecated, and we are replacing them with 
>> flexible
>> array members instead. So, replace one-element array with flexible-array
>> member in struct vfio_ccw_parent and refactor the the rest of the code
>> accordingly.
>>
>> Link: https://github.com/KSPP/linux/issues/79
>> Link: https://github.com/KSPP/linux/issues/297
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>> ---
>>   drivers/s390/cio/vfio_ccw_drv.c     | 3 ++-
>>   drivers/s390/cio/vfio_ccw_private.h | 2 +-
>>   2 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/s390/cio/vfio_ccw_drv.c 
>> b/drivers/s390/cio/vfio_ccw_drv.c
>> index ff538a086fc7..57906a9c6324 100644
>> --- a/drivers/s390/cio/vfio_ccw_drv.c
>> +++ b/drivers/s390/cio/vfio_ccw_drv.c
>> @@ -171,7 +171,8 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
>>           return -ENODEV;
>>       }
>> -    parent = kzalloc(sizeof(*parent), GFP_KERNEL);
>> +    parent = kzalloc(sizeof(*parent) + sizeof(struct mdev_type *),
> 
> Hi, wouldn't:
> 
>     parent = kzalloc(struct_size(parent, mdev_types, 1)),
> 
> be more informative and in the spirit of flexible array use?

Ok, patch 2/2.

Sorry for the noise.

CJ

> 
> Just my 2c,
> 
> CJ
> 
>> +             GFP_KERNEL);
>>       if (!parent)
>>           return -ENOMEM;
>> diff --git a/drivers/s390/cio/vfio_ccw_private.h 
>> b/drivers/s390/cio/vfio_ccw_private.h
>> index b441ae6700fd..b62bbc5c6376 100644
>> --- a/drivers/s390/cio/vfio_ccw_private.h
>> +++ b/drivers/s390/cio/vfio_ccw_private.h
>> @@ -79,7 +79,7 @@ struct vfio_ccw_parent {
>>       struct mdev_parent    parent;
>>       struct mdev_type    mdev_type;
>> -    struct mdev_type    *mdev_types[1];
>> +    struct mdev_type    *mdev_types[];
>>   };
>>   /**
> 
>