linux-kernel - Re: [PATCH v2] crypto: ccp - Use kzalloc for sev ioctl interfaces to prevent kernel memory leak

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Message-ID: <CAMkAt6oUxUFtNS4W0bzu13oWMdfnzfNrphH3OqwAkmxJcXhOqw@mail.gmail.com>
Date:   Mon, 16 May 2022 08:53:16 -0700
From:   Peter Gonda <pgonda@...gle.com>
To:     John Allen <john.allen@....com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        Ashish Kalra <Ashish.Kalra@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Nguyen <theflow@...gle.com>,
        David Rientjes <rientjes@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] crypto: ccp - Use kzalloc for sev ioctl interfaces to
 prevent kernel memory leak

On Mon, May 16, 2022 at 8:46 AM John Allen <john.allen@....com> 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.
>
> Fixes: e799035609e15 ("crypto: ccp: Implement SEV_PEK_CSR ioctl command")
> Fixes: 76a2b524a4b1d ("crypto: ccp: Implement SEV_PDH_CERT_EXPORT ioctl command")
> Fixes: d6112ea0cb344 ("crypto: ccp - introduce SEV_GET_ID2 command")
> Cc: stable@...r.kernel.org
> Reported-by: Andy Nguyen <theflow@...gle.com>
> Suggested-by: David Rientjes <rientjes@...gle.com>
> Suggested-by: Peter Gonda <pgonda@...gle.com>
> Signed-off-by: John Allen <john.allen@....com>
> ---
> v2:
>   - Add fixes tags and CC stable@...r.kernel.org
> ---


static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp)
{
struct sev_user_data_status data;
int ret;

ret = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, &data, &argp->error);
if (ret)
return ret;

if (copy_to_user((void __user *)argp->data, &data, sizeof(data)))
ret = -EFAULT;

return ret;
}

Would it be safer to memset @data here to all zeros too?