linux-kernel - Re: [PATCH 1/1] crypto: Fix possible buffer overflows in pkey_protkey_aes_attr

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Message-ID: <04b376ce-bb1c-f7ff-a41a-8905badd9dba@de.ibm.com>
Date:   Wed, 9 Dec 2020 07:54:22 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] crypto: Fix possible buffer overflows in
 pkey_protkey_aes_attr_read



On 09.12.20 07:47, Xiaohui Zhang wrote:
> From: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> 
> pkey_protkey_aes_attr_read() calls memcpy() without checking the
> destination size may trigger a buffer overflower.

To me it looks like protkey.len is generated programmatically in pkey_genprotkey/pkey_clr2protkey
and this purely depends on the keytype and we do check for known ones.
Not sure how this can happen.

> 
> Signed-off-by: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> ---
>  drivers/s390/crypto/pkey_api.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
> index 99cb60ea6..abc237130 100644
> --- a/drivers/s390/crypto/pkey_api.c
> +++ b/drivers/s390/crypto/pkey_api.c
> @@ -1589,6 +1589,8 @@ static ssize_t pkey_protkey_aes_attr_read(u32 keytype, bool is_xts, char *buf,
>  	if (rc)
>  		return rc;
>  
> +	if (protkey.len > MAXPROTKEYSIZE)
> +		protkey.len = MAXPROTKEYSIZE;
>  	protkeytoken.len = protkey.len;
>  	memcpy(&protkeytoken.protkey, &protkey.protkey, protkey.len);
>  
> @@ -1599,6 +1601,8 @@ static ssize_t pkey_protkey_aes_attr_read(u32 keytype, bool is_xts, char *buf,
>  		if (rc)
>  			return rc;
>  
> +		if (protkey.len > MAXPROTKEYSIZE)
> +			protkey.len = MAXPROTKEYSIZE;
>  		protkeytoken.len = protkey.len;
>  		memcpy(&protkeytoken.protkey, &protkey.protkey, protkey.len);
>  
>