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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id p4sm7982027edr.43.2021.04.17.05.40.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 17 Apr 2021 05:40:40 -0700 (PDT) Subject: Re: [PATCH v2 5/8] crypto: ccp: Use the stack for small SEV command buffers To: Sean Christopherson , Brijesh Singh , Tom Lendacky , John Allen Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Christophe Leroy References: <20210406224952.4177376-1-seanjc@google.com> <20210406224952.4177376-6-seanjc@google.com> From: Paolo Bonzini Message-ID: <587677cf-2db1-1bed-18fc-dbbc1c1dffed@redhat.com> Date: Sat, 17 Apr 2021 14:40:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210406224952.4177376-6-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/21 00:49, Sean Christopherson wrote: > For commands with small input/output buffers, use the local stack to > "allocate" the structures used to communicate with the PSP. Now that > __sev_do_cmd_locked() gracefully handles vmalloc'd buffers, there's no > reason to avoid using the stack, e.g. CONFIG_VMAP_STACK=y will just work. > > Signed-off-by: Sean Christopherson Squashing this in (inspired by Christophe's review, though not quite matching his suggestion). diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 0f5644a3b138..246b281b6376 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -408,12 +408,11 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable) if (copy_from_user(&input, (void __user *)argp->data, sizeof(input))) return -EFAULT; + memset(&data, 0, sizeof(data)); + /* userspace wants to query CSR length */ - if (!input.address || !input.length) { - data.address = 0; - data.len = 0; + if (!input.address || !input.length) goto cmd; - } /* allocate a physically contiguous buffer to store the CSR blob */ input_address = (void __user *)input.address;