[PATCH 5/5] KVM: SVM: Allocate SEV command structures on local stack

Sean Christopherson
2021-04-02T23:37:45Z

Use the local stack to "allocate" the structures used to communicate with
the PSP. The largest struct used by KVM, sev_data_launch_secret, clocks
in at 52 bytes, well within the realm of reasonable stack usage. The
smallest structs are a mere 4 bytes, i.e. the pointer for the allocation
is larger than the allocation itself.

Now that the PSP driver plays nice with vmalloc pointers, putting the
data on a virtually mapped stack (CONFIG_VMAP_STACK=y) will not cause
explosions.

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/sev.c | 262 +++++++++++++++--------------------------
1 file changed, 96 insertions(+), 166 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5457138c7347..316fd39c7aef 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -150,35 +150,22 @@ static void sev_asid_free(int asid)

static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
{
- struct sev_data_decommission *decommission;
- struct sev_data_deactivate *data;
+ struct sev_data_decommission decommission;
+ struct sev_data_deactivate deactivate;

if (!handle)
return;

- data = kzalloc(sizeof(*data), GFP_KERNEL);
- if (!data)
- return;
-
- /* deactivate handle */
- data->handle = handle;
+ deactivate.handle = handle;

/* Guard DEACTIVATE against WBINVD/DF_FLUSH used in ASID recycling */
down_read(&sev_deactivate_lock);
- sev_guest_deactivate(data, NULL);
+ sev_guest_deactivate(&deactivate, NULL);
up_read(&sev_deactivate_lock);

- kfree(data);
-
- decommission = kzalloc(sizeof(*decommission), GFP_KERNEL);
- if (!decommission)
- return;
-
/* decommission handle */
- decommission->handle = handle;
- sev_guest_decommission(decommission, NULL);
-
- kfree(decommission);
+ decommission.handle = handle;
+ sev_guest_decommission(&decommission, NULL);
}

static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
@@ -216,19 +203,14 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)

static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
{
- struct sev_data_activate *data;
+ struct sev_data_activate activate;
int asid = sev_get_asid(kvm);
int ret;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
-
/* activate ASID on the given handle */
- data->handle = handle;
- data->asid = asid;
- ret = sev_guest_activate(data, error);
- kfree(data);
+ activate.handle = handle;
+ activate.asid = asid;
+ ret = sev_guest_activate(&activate, error);

return ret;
}
@@ -258,7 +240,7 @@ static int sev_issue_cmd(struct kvm *kvm, int id, void *data, int *error)
static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_launch_start *start;
+ struct sev_data_launch_start start;
struct kvm_sev_launch_start params;
void *dh_blob, *session_blob;
int *error = &argp->error;
@@ -270,20 +252,16 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
return -EFAULT;

- start = kzalloc(sizeof(*start), GFP_KERNEL_ACCOUNT);
- if (!start)
- return -ENOMEM;
+ memset(&start, 0, sizeof(start));

dh_blob = NULL;
if (params.dh_uaddr) {
dh_blob = psp_copy_user_blob(params.dh_uaddr, params.dh_len);
- if (IS_ERR(dh_blob)) {
- ret = PTR_ERR(dh_blob);
- goto e_free;
- }
+ if (IS_ERR(dh_blob))
+ return PTR_ERR(dh_blob);

- start->dh_cert_address = __sme_set(__pa(dh_blob));
- start->dh_cert_len = params.dh_len;
+ start.dh_cert_address = __sme_set(__pa(dh_blob));
+ start.dh_cert_len = params.dh_len;
}

session_blob = NULL;
@@ -294,40 +272,38 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
goto e_free_dh;
}

- start->session_address = __sme_set(__pa(session_blob));
- start->session_len = params.session_len;
+ start.session_address = __sme_set(__pa(session_blob));
+ start.session_len = params.session_len;
}

- start->handle = params.handle;
- start->policy = params.policy;
+ start.handle = params.handle;
+ start.policy = params.policy;

/* create memory encryption context */
- ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_LAUNCH_START, start, error);
+ ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_LAUNCH_START, &start, error);
if (ret)
goto e_free_session;

/* Bind ASID to this guest */
- ret = sev_bind_asid(kvm, start->handle, error);
+ ret = sev_bind_asid(kvm, start.handle, error);
if (ret)
goto e_free_session;

/* return handle to userspace */
- params.handle = start->handle;
+ params.handle = start.handle;
if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params))) {
- sev_unbind_asid(kvm, start->handle);
+ sev_unbind_asid(kvm, start.handle);
ret = -EFAULT;
goto e_free_session;
}

- sev->handle = start->handle;
+ sev->handle = start.handle;
sev->fd = argp->sev_fd;

e_free_session:
kfree(session_blob);
e_free_dh:
kfree(dh_blob);
-e_free:
- kfree(start);
return ret;
}

@@ -446,7 +422,7 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
unsigned long vaddr, vaddr_end, next_vaddr, npages, pages, size, i;
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
struct kvm_sev_launch_update_data params;
- struct sev_data_launch_update_data *data;
+ struct sev_data_launch_update_data data;
struct page **inpages;
int ret;

@@ -456,20 +432,14 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
return -EFAULT;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
-
vaddr = params.uaddr;
size = params.len;
vaddr_end = vaddr + size;

/* Lock the user memory. */
inpages = sev_pin_memory(kvm, vaddr, size, &npages, 1);
- if (IS_ERR(inpages)) {
- ret = PTR_ERR(inpages);
- goto e_free;
- }
+ if (IS_ERR(inpages))
+ return PTR_ERR(inpages);

/*
* Flush (on non-coherent CPUs) before LAUNCH_UPDATE encrypts pages in
@@ -477,6 +447,9 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
*/
sev_clflush_pages(inpages, npages);

+ data.reserved = 0;
+ data.handle = sev->handle;
+
for (i = 0; vaddr < vaddr_end; vaddr = next_vaddr, i += pages) {
int offset, len;

@@ -491,10 +464,9 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)

len = min_t(size_t, ((pages * PAGE_SIZE) - offset), size);

- data->handle = sev->handle;
- data->len = len;
- data->address = __sme_page_pa(inpages[i]) + offset;
- ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_DATA, data, &argp->error);
+ data.len = len;
+ data.address = __sme_page_pa(inpages[i]) + offset;
+ ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_DATA, &data, &argp->error);
if (ret)
goto e_unpin;

@@ -510,8 +482,6 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
}
/* unlock the user pages */
sev_unpin_memory(kvm, inpages, npages);
-e_free:
- kfree(data);
return ret;
}

@@ -563,16 +533,14 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_launch_update_vmsa *vmsa;
+ struct sev_data_launch_update_vmsa vmsa;
struct kvm_vcpu *vcpu;
int i, ret;

if (!sev_es_guest(kvm))
return -ENOTTY;

- vmsa = kzalloc(sizeof(*vmsa), GFP_KERNEL);
- if (!vmsa)
- return -ENOMEM;
+ vmsa.reserved = 0;

kvm_for_each_vcpu(i, vcpu, kvm) {
struct vcpu_svm *svm = to_svm(vcpu);
@@ -580,7 +548,7 @@ static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
/* Perform some pre-encryption checks against the VMSA */
ret = sev_es_sync_vmsa(svm);
if (ret)
- goto e_free;
+ return ret;

/*
* The LAUNCH_UPDATE_VMSA command will perform in-place
@@ -590,27 +558,25 @@ static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
*/
clflush_cache_range(svm->vmsa, PAGE_SIZE);

- vmsa->handle = sev->handle;
- vmsa->address = __sme_pa(svm->vmsa);
- vmsa->len = PAGE_SIZE;
- ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_VMSA, vmsa,
+ vmsa.handle = sev->handle;
+ vmsa.address = __sme_pa(svm->vmsa);
+ vmsa.len = PAGE_SIZE;
+ ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_VMSA, &vmsa,
&argp->error);
if (ret)
- goto e_free;
+ return ret;

svm->vcpu.arch.guest_state_protected = true;
}

-e_free:
- kfree(vmsa);
- return ret;
+ return 0;
}

static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
void __user *measure = (void __user *)(uintptr_t)argp->data;
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_launch_measure *data;
+ struct sev_data_launch_measure data;
struct kvm_sev_launch_measure params;
void __user *p = NULL;
void *blob = NULL;
@@ -622,9 +588,7 @@ static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (copy_from_user(&params, measure, sizeof(params)))
return -EFAULT;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
+ memset(&data, 0, sizeof(data));

/* User wants to query the blob length */
if (!params.len)
@@ -632,23 +596,20 @@ static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)

p = (void __user *)(uintptr_t)params.uaddr;
if (p) {
- if (params.len > SEV_FW_BLOB_MAX_SIZE) {
- ret = -EINVAL;
- goto e_free;
- }
+ if (params.len > SEV_FW_BLOB_MAX_SIZE)
+ return -EINVAL;

- ret = -ENOMEM;
blob = kmalloc(params.len, GFP_KERNEL_ACCOUNT);
if (!blob)
- goto e_free;
+ return -ENOMEM;

- data->address = __psp_pa(blob);
- data->len = params.len;
+ data.address = __psp_pa(blob);
+ data.len = params.len;
}

cmd:
- data->handle = sev->handle;
- ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_MEASURE, data, &argp->error);
+ data.handle = sev->handle;
+ ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_MEASURE, &data, &argp->error);

/*
* If we query the session length, FW responded with expected data.
@@ -665,63 +626,50 @@ static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
}

done:
- params.len = data->len;
+ params.len = data.len;
if (copy_to_user(measure, &params, sizeof(params)))
ret = -EFAULT;
e_free_blob:
kfree(blob);
-e_free:
- kfree(data);
return ret;
}

static int sev_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_launch_finish *data;
- int ret;
+ struct sev_data_launch_finish data;

if (!sev_guest(kvm))
return -ENOTTY;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
-
- data->handle = sev->handle;
- ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_FINISH, data, &argp->error);
-
- kfree(data);
- return ret;
+ data.handle = sev->handle;
+ return sev_issue_cmd(kvm, SEV_CMD_LAUNCH_FINISH, &data, &argp->error);
}

static int sev_guest_status(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
struct kvm_sev_guest_status params;
- struct sev_data_guest_status *data;
+ struct sev_data_guest_status data;
int ret;

if (!sev_guest(kvm))
return -ENOTTY;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
+ memset(&data, 0, sizeof(data));

- data->handle = sev->handle;
- ret = sev_issue_cmd(kvm, SEV_CMD_GUEST_STATUS, data, &argp->error);
+ data.handle = sev->handle;
+ ret = sev_issue_cmd(kvm, SEV_CMD_GUEST_STATUS, &data, &argp->error);
if (ret)
- goto e_free;
+ return ret;

- params.policy = data->policy;
- params.state = data->state;
- params.handle = data->handle;
+ params.policy = data.policy;
+ params.state = data.state;
+ params.handle = data.handle;

if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params)))
ret = -EFAULT;
-e_free:
- kfree(data);
+
return ret;
}

@@ -730,23 +678,17 @@ static int __sev_issue_dbg_cmd(struct kvm *kvm, unsigned long src,
int *error, bool enc)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_dbg *data;
- int ret;
+ struct sev_data_dbg data;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
+ data.reserved = 0;
+ data.handle = sev->handle;
+ data.dst_addr = dst;
+ data.src_addr = src;
+ data.len = size;

- data->handle = sev->handle;
- data->dst_addr = dst;
- data->src_addr = src;
- data->len = size;
-
- ret = sev_issue_cmd(kvm,
- enc ? SEV_CMD_DBG_ENCRYPT : SEV_CMD_DBG_DECRYPT,
- data, error);
- kfree(data);
- return ret;
+ return sev_issue_cmd(kvm,
+ enc ? SEV_CMD_DBG_ENCRYPT : SEV_CMD_DBG_DECRYPT,
+ &data, error);
}

static int __sev_dbg_decrypt(struct kvm *kvm, unsigned long src_paddr,
@@ -966,7 +908,7 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_launch_secret *data;
+ struct sev_data_launch_secret data;
struct kvm_sev_launch_secret params;
struct page **pages;
void *blob, *hdr;
@@ -998,41 +940,36 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
goto e_unpin_memory;
}

- ret = -ENOMEM;
- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- goto e_unpin_memory;
+ memset(&data, 0, sizeof(data));

offset = params.guest_uaddr & (PAGE_SIZE - 1);
- data->guest_address = __sme_page_pa(pages[0]) + offset;
- data->guest_len = params.guest_len;
+ data.guest_address = __sme_page_pa(pages[0]) + offset;
+ data.guest_len = params.guest_len;

blob = psp_copy_user_blob(params.trans_uaddr, params.trans_len);
if (IS_ERR(blob)) {
ret = PTR_ERR(blob);
- goto e_free;
+ goto e_unpin_memory;
}

- data->trans_address = __psp_pa(blob);
- data->trans_len = params.trans_len;
+ data.trans_address = __psp_pa(blob);
+ data.trans_len = params.trans_len;

hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);
if (IS_ERR(hdr)) {
ret = PTR_ERR(hdr);
goto e_free_blob;
}
- data->hdr_address = __psp_pa(hdr);
- data->hdr_len = params.hdr_len;
+ data.hdr_address = __psp_pa(hdr);
+ data.hdr_len = params.hdr_len;

- data->handle = sev->handle;
- ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_SECRET, data, &argp->error);
+ data.handle = sev->handle;
+ ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_SECRET, &data, &argp->error);

kfree(hdr);

e_free_blob:
kfree(blob);
-e_free:
- kfree(data);
e_unpin_memory:
/* content of memory is updated, mark pages dirty */
for (i = 0; i < n; i++) {
@@ -1047,7 +984,7 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
void __user *report = (void __user *)(uintptr_t)argp->data;
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
- struct sev_data_attestation_report *data;
+ struct sev_data_attestation_report data;
struct kvm_sev_attestation_report params;
void __user *p;
void *blob = NULL;
@@ -1059,9 +996,7 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
return -EFAULT;

- data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
- if (!data)
- return -ENOMEM;
+ memset(&data, 0, sizeof(data));

/* User wants to query the blob length */
if (!params.len)
@@ -1069,23 +1004,20 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)

p = (void __user *)(uintptr_t)params.uaddr;
if (p) {
- if (params.len > SEV_FW_BLOB_MAX_SIZE) {
- ret = -EINVAL;
- goto e_free;
- }
+ if (params.len > SEV_FW_BLOB_MAX_SIZE)
+ return -EINVAL;

- ret = -ENOMEM;
blob = kmalloc(params.len, GFP_KERNEL_ACCOUNT);
if (!blob)
- goto e_free;
+ return -ENOMEM;

- data->address = __psp_pa(blob);
- data->len = params.len;
- memcpy(data->mnonce, params.mnonce, sizeof(params.mnonce));
+ data.address = __psp_pa(blob);
+ data.len = params.len;
+ memcpy(data.mnonce, params.mnonce, sizeof(params.mnonce));
}
cmd:
- data->handle = sev->handle;
- ret = sev_issue_cmd(kvm, SEV_CMD_ATTESTATION_REPORT, data, &argp->error);
+ data.handle = sev->handle;
+ ret = sev_issue_cmd(kvm, SEV_CMD_ATTESTATION_REPORT, &data, &argp->error);
/*
* If we query the session length, FW responded with expected data.
*/
@@ -1101,13 +1033,11 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
}

done:
- params.len = data->len;
+ params.len = data.len;
if (copy_to_user(report, &params, sizeof(params)))
ret = -EFAULT;
e_free_blob:
kfree(blob);
-e_free:
- kfree(data);
return ret;
}

--
2.31.0.208.g409f899ff0-goog