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Date: Wed, 7 Apr 2021 07:18:13 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Brijesh Singh <brijesh.singh@....com>,
Tom Lendacky <thomas.lendacky@....com>,
John Allen <john.allen@....com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH v2 5/8] crypto: ccp: Use the stack for small SEV command
buffers
Le 07/04/2021 à 00:49, Sean Christopherson a écrit :
> 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 <seanjc@...gle.com>
> ---
> drivers/crypto/ccp/sev-dev.c | 122 ++++++++++++++---------------------
> 1 file changed, 47 insertions(+), 75 deletions(-)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 4aedbdaffe90..bb0d6de071e6 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -396,7 +396,7 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
> {
> struct sev_device *sev = psp_master->sev_data;
> struct sev_user_data_pek_csr input;
> - struct sev_data_pek_csr *data;
> + struct sev_data_pek_csr data;
struct sev_data_pek_csr data = {0, 0};
> void __user *input_address;
> void *blob = NULL;
> int ret;
> @@ -407,29 +407,24 @@ 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;
>
> - data = kzalloc(sizeof(*data), GFP_KERNEL);
> - if (!data)
> - return -ENOMEM;
> -
> /* userspace wants to query CSR length */
> - if (!input.address || !input.length)
> + if (!input.address || !input.length) {
> + data.address = 0;
> + data.len = 0;
With the change proposed above, those two new lines are unneeded.
> goto cmd;
> + }
>
> /* allocate a physically contiguous buffer to store the CSR blob */
> input_address = (void __user *)input.address;
> - if (input.length > SEV_FW_BLOB_MAX_SIZE) {
> - ret = -EFAULT;
> - goto e_free;
> - }
> + if (input.length > SEV_FW_BLOB_MAX_SIZE)
> + return -EFAULT;
>
> blob = kmalloc(input.length, GFP_KERNEL);
> - if (!blob) {
> - ret = -ENOMEM;
> - goto e_free;
> - }
> + if (!blob)
> + return -ENOMEM;
>
> - data->address = __psp_pa(blob);
> - data->len = input.length;
> + data.address = __psp_pa(blob);
> + data.len = input.length;
>
> cmd:
> if (sev->state == SEV_STATE_UNINIT) {
> @@ -438,10 +433,10 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
> goto e_free_blob;
> }
>
> - ret = __sev_do_cmd_locked(SEV_CMD_PEK_CSR, data, &argp->error);
> + ret = __sev_do_cmd_locked(SEV_CMD_PEK_CSR, &data, &argp->error);
>
> /* If we query the CSR length, FW responded with expected data. */
> - input.length = data->len;
> + input.length = data.len;
>
> if (copy_to_user((void __user *)argp->data, &input, sizeof(input))) {
> ret = -EFAULT;
> @@ -455,8 +450,6 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
>
> e_free_blob:
> kfree(blob);
> -e_free:
> - kfree(data);
> return ret;
> }
>
> @@ -588,7 +581,7 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
> {
> struct sev_device *sev = psp_master->sev_data;
> struct sev_user_data_pek_cert_import input;
> - struct sev_data_pek_cert_import *data;
> + struct sev_data_pek_cert_import data;
> void *pek_blob, *oca_blob;
> int ret;
>
> @@ -598,19 +591,14 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
> if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
> return -EFAULT;
>
> - data = kzalloc(sizeof(*data), GFP_KERNEL);
> - if (!data)
> - return -ENOMEM;
> -
> /* copy PEK certificate blobs from userspace */
> pek_blob = psp_copy_user_blob(input.pek_cert_address, input.pek_cert_len);
> - if (IS_ERR(pek_blob)) {
> - ret = PTR_ERR(pek_blob);
> - goto e_free;
> - }
> + if (IS_ERR(pek_blob))
> + return PTR_ERR(pek_blob);
>
> - data->pek_cert_address = __psp_pa(pek_blob);
> - data->pek_cert_len = input.pek_cert_len;
> + data.reserved = 0;
> + data.pek_cert_address = __psp_pa(pek_blob);
> + data.pek_cert_len = input.pek_cert_len;
>
> /* copy PEK certificate blobs from userspace */
> oca_blob = psp_copy_user_blob(input.oca_cert_address, input.oca_cert_len);
> @@ -619,8 +607,8 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
> goto e_free_pek;
> }
>
> - data->oca_cert_address = __psp_pa(oca_blob);
> - data->oca_cert_len = input.oca_cert_len;
> + data.oca_cert_address = __psp_pa(oca_blob);
> + data.oca_cert_len = input.oca_cert_len;
>
> /* If platform is not in INIT state then transition it to INIT */
> if (sev->state != SEV_STATE_INIT) {
> @@ -629,21 +617,19 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
> goto e_free_oca;
> }
>
> - ret = __sev_do_cmd_locked(SEV_CMD_PEK_CERT_IMPORT, data, &argp->error);
> + ret = __sev_do_cmd_locked(SEV_CMD_PEK_CERT_IMPORT, &data, &argp->error);
>
> e_free_oca:
> kfree(oca_blob);
> e_free_pek:
> kfree(pek_blob);
> -e_free:
> - kfree(data);
> return ret;
> }
>
> static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
> {
> struct sev_user_data_get_id2 input;
> - struct sev_data_get_id *data;
> + struct sev_data_get_id data;
> void __user *input_address;
> void *id_blob = NULL;
> int ret;
> @@ -657,28 +643,25 @@ static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
>
> input_address = (void __user *)input.address;
>
> - data = kzalloc(sizeof(*data), GFP_KERNEL);
> - if (!data)
> - return -ENOMEM;
> -
> if (input.address && input.length) {
> id_blob = kmalloc(input.length, GFP_KERNEL);
> - if (!id_blob) {
> - kfree(data);
> + if (!id_blob)
> return -ENOMEM;
> - }
>
> - data->address = __psp_pa(id_blob);
> - data->len = input.length;
> + data.address = __psp_pa(id_blob);
> + data.len = input.length;
> + } else {
> + data.address = 0;
> + data.len = 0;
> }
>
> - ret = __sev_do_cmd_locked(SEV_CMD_GET_ID, data, &argp->error);
> + ret = __sev_do_cmd_locked(SEV_CMD_GET_ID, &data, &argp->error);
>
> /*
> * Firmware will return the length of the ID value (either the minimum
> * required length or the actual length written), return it to the user.
> */
> - input.length = data->len;
> + input.length = data.len;
>
> if (copy_to_user((void __user *)argp->data, &input, sizeof(input))) {
> ret = -EFAULT;
> @@ -686,7 +669,7 @@ static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
> }
>
> if (id_blob) {
> - if (copy_to_user(input_address, id_blob, data->len)) {
> + if (copy_to_user(input_address, id_blob, data.len)) {
> ret = -EFAULT;
> goto e_free;
> }
> @@ -694,7 +677,6 @@ static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
>
> e_free:
> kfree(id_blob);
> - kfree(data);
>
> return ret;
> }
> @@ -744,7 +726,7 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
> struct sev_device *sev = psp_master->sev_data;
> struct sev_user_data_pdh_cert_export input;
> void *pdh_blob = NULL, *cert_blob = NULL;
> - struct sev_data_pdh_cert_export *data;
> + struct sev_data_pdh_cert_export data;
struct sev_data_pdh_cert_export data = {0, 0, 0, 0, 0};
> void __user *input_cert_chain_address;
> void __user *input_pdh_cert_address;
> int ret;
> @@ -762,9 +744,7 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
> if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
> return -EFAULT;
>
> - data = kzalloc(sizeof(*data), GFP_KERNEL);
> - if (!data)
> - return -ENOMEM;
> + memset(&data, 0, sizeof(data));
You can avoid that memset by initing at declaration, see above.
>
> /* Userspace wants to query the certificate length. */
> if (!input.pdh_cert_address ||
> @@ -776,25 +756,19 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
> input_cert_chain_address = (void __user *)input.cert_chain_address;
>
> /* Allocate a physically contiguous buffer to store the PDH blob. */
> - if (input.pdh_cert_len > SEV_FW_BLOB_MAX_SIZE) {
> - ret = -EFAULT;
> - goto e_free;
> - }
> + if (input.pdh_cert_len > SEV_FW_BLOB_MAX_SIZE)
> + return -EFAULT;
>
> /* Allocate a physically contiguous buffer to store the cert chain blob. */
> - if (input.cert_chain_len > SEV_FW_BLOB_MAX_SIZE) {
> - ret = -EFAULT;
> - goto e_free;
> - }
> + if (input.cert_chain_len > SEV_FW_BLOB_MAX_SIZE)
> + return -EFAULT;
>
> pdh_blob = kmalloc(input.pdh_cert_len, GFP_KERNEL);
> - if (!pdh_blob) {
> - ret = -ENOMEM;
> - goto e_free;
> - }
> + if (!pdh_blob)
> + return -ENOMEM;
>
> - data->pdh_cert_address = __psp_pa(pdh_blob);
> - data->pdh_cert_len = input.pdh_cert_len;
> + 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);
> if (!cert_blob) {
> @@ -802,15 +776,15 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
> goto e_free_pdh;
> }
>
> - data->cert_chain_address = __psp_pa(cert_blob);
> - data->cert_chain_len = input.cert_chain_len;
> + data.cert_chain_address = __psp_pa(cert_blob);
> + data.cert_chain_len = input.cert_chain_len;
>
> cmd:
> - ret = __sev_do_cmd_locked(SEV_CMD_PDH_CERT_EXPORT, data, &argp->error);
> + ret = __sev_do_cmd_locked(SEV_CMD_PDH_CERT_EXPORT, &data, &argp->error);
>
> /* If we query the length, FW responded with expected data. */
> - input.cert_chain_len = data->cert_chain_len;
> - input.pdh_cert_len = data->pdh_cert_len;
> + input.cert_chain_len = data.cert_chain_len;
> + input.pdh_cert_len = data.pdh_cert_len;
>
> if (copy_to_user((void __user *)argp->data, &input, sizeof(input))) {
> ret = -EFAULT;
> @@ -835,8 +809,6 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
> kfree(cert_blob);
> e_free_pdh:
> kfree(pdh_blob);
> -e_free:
> - kfree(data);
> return ret;
> }
>
>
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