Re: [PATCH v2] s390/pkey: prevent overflow in size calculation for memdup_user()

[Holger Dengler <dengler@linux.ibm.com>]

On 11/06/2025 21:20, Fedor Pchelkin wrote:
> Number of apqn target list entries contained in 'nr_apqns' variable is
> determined by userspace via an ioctl call so the result of the product in
> calculation of size passed to memdup_user() may overflow.
> 
> In this case the actual size of the allocated area and the value
> describing it won't be in sync leading to various types of unpredictable
> behaviour later.
> 
> Use a proper memdup_array_user() helper which returns an error if an
> overflow is detected. Note that it is different from when nr_apqns is
> initially zero - that case is considered valid and should be handled in
> subsequent pkey_handler implementations.
> 
> Found by Linux Verification Center (linuxtesting.org).
> 
> Fixes: f2bbc96e7cfa ("s390/pkey: add CCA AES cipher key support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>

Reviewed-by: Holger Dengler <dengler@linux.ibm.com>

-- 
Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
dengler@linux.ibm.com