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

[Alexander Gordeev]

On Wed, Jun 11, 2025 at 10:20:10PM +0300, 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@xxxxxxxxxxxxxxx
> Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
> ---
> 
> v2: use memdup_array_user() helper (Heiko Carstens)
> 
>  drivers/s390/crypto/pkey_api.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
> index cef60770f68b..b3fcdcae379e 100644
> --- a/drivers/s390/crypto/pkey_api.c
> +++ b/drivers/s390/crypto/pkey_api.c
> @@ -86,7 +86,7 @@ static void *_copy_apqns_from_user(void __user *uapqns, size_t nr_apqns)
>  	if (!uapqns || nr_apqns == 0)
>  		return NULL;
>  
> -	return memdup_user(uapqns, nr_apqns * sizeof(struct pkey_apqn));
> +	return memdup_array_user(uapqns, nr_apqns, sizeof(struct pkey_apqn));
>  }
>  
>  static int pkey_ioctl_genseck(struct pkey_genseck __user *ugs)

Applied, thanks!