linux-kernel - Re: [PATCH v2] s390/pkey: prevent overflow in size calculation for memdup

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Message-ID: <aEq8wrEmJVItMiZQ@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Thu, 12 Jun 2025 13:40:50 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Fedor Pchelkin <pchelkin@...ras.ru>
Cc: Harald Freudenberger <freude@...ux.ibm.com>,
        Holger Dengler <dengler@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Ingo Franzki <ifranzki@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] s390/pkey: prevent overflow in size calculation for
 memdup_user()

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@...r.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> ---
> 
> 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!