Re: [PATCH] crypto: ccp - Use kzalloc for sev ioctl interfaces to prevent kernel memory leak

[John Allen <john.allen@amd.com>]

On Thu, May 12, 2022 at 08:34:55PM +0000, John Allen wrote:
> For some sev ioctl interfaces, input may be passed that is less than or
> equal to SEV_FW_BLOB_MAX_SIZE, but larger than the data that PSP
> firmware returns. In this case, kmalloc will allocate memory that is the
> size of the input rather than the size of the data. Since PSP firmware
> doesn't fully overwrite the buffer, the sev ioctl interfaces with the
> issue may return uninitialized slab memory.
> 
> Currently, all of the ioctl interfaces in the ccp driver are safe, but
> to prevent future problems, change all ioctl interfaces that allocate
> memory with kmalloc to use kzalloc.

I should have CC'd stable@vger.kernel.org and added a Fixes tag for
this. I'll send a v2 with these, but I'll give it a couple days for
comments before I do.

Thanks,
John

> 
> Reported-by: Andy Nguyen <theflow@google.com>
> Suggested-by: David Rientjes <rientjes@google.com>
> Suggested-by: Peter Gonda <pgonda@google.com>
> Signed-off-by: John Allen <john.allen@amd.com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 6ab93dfd478a..e2298843ea8a 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -604,7 +604,7 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
>  	if (input.length > SEV_FW_BLOB_MAX_SIZE)
>  		return -EFAULT;
>  
> -	blob = kmalloc(input.length, GFP_KERNEL);
> +	blob = kzalloc(input.length, GFP_KERNEL);
>  	if (!blob)
>  		return -ENOMEM;
>  
> @@ -828,7 +828,7 @@ static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
>  	input_address = (void __user *)input.address;
>  
>  	if (input.address && input.length) {
> -		id_blob = kmalloc(input.length, GFP_KERNEL);
> +		id_blob = kzalloc(input.length, GFP_KERNEL);
>  		if (!id_blob)
>  			return -ENOMEM;
>  
> @@ -947,14 +947,14 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
>  	if (input.cert_chain_len > SEV_FW_BLOB_MAX_SIZE)
>  		return -EFAULT;
>  
> -	pdh_blob = kmalloc(input.pdh_cert_len, GFP_KERNEL);
> +	pdh_blob = kzalloc(input.pdh_cert_len, GFP_KERNEL);
>  	if (!pdh_blob)
>  		return -ENOMEM;
>  
>  	data.pdh_cert_address = __psp_pa(pdh_blob);
>  	data.pdh_cert_len = input.pdh_cert_len;
>  
> -	cert_blob = kmalloc(input.cert_chain_len, GFP_KERNEL);
> +	cert_blob = kzalloc(input.cert_chain_len, GFP_KERNEL);
>  	if (!cert_blob) {
>  		ret = -ENOMEM;
>  		goto e_free_pdh;
> -- 
> 2.34.1
>