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KVM: SVM: no need to call access_ok() in LAUNCH_MEASURE command 

Using the access_ok() to validate the input before issuing the SEV
command does not buy us anything in this case. If userland is
giving us a garbage pointer then copy_to_user() will catch it when we try
to return the measurement.

Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Fixes: 0d0736f763 (KVM: SVM: Add support for KVM_SEV_LAUNCH_MEASURE ...)
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-kernel@vger.kernel.org
Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Brijesh Singh 2018-02-23 12:36:50 -06:00 committed by Paolo Bonzini
parent 45d0be8763
commit 3e233385ef
1 changed files with 7 additions and 9 deletions
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16
arch/x86/kvm/svm.c
View File

@ -6236,16 +6236,18 @@ e_free:
static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp) 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 = &kvm->arch.sev_info; struct kvm_sev_info *sev = &kvm->arch.sev_info;
struct sev_data_launch_measure *data; struct sev_data_launch_measure *data;
struct kvm_sev_launch_measure params; struct kvm_sev_launch_measure params;
void __user *p = NULL;
void *blob = NULL; void *blob = NULL;
int ret; int ret;
if (!sev_guest(kvm)) if (!sev_guest(kvm))
return -ENOTTY; return -ENOTTY;
if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params))) if (copy_from_user(&params, measure, sizeof(params)))
return -EFAULT; return -EFAULT;
data = kzalloc(sizeof(*data), GFP_KERNEL); data = kzalloc(sizeof(*data), GFP_KERNEL);
@ -6256,17 +6258,13 @@ static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (!params.len) if (!params.len)
goto cmd; goto cmd;
if (params.uaddr) { p = (void __user *)(uintptr_t)params.uaddr;
if (p) {
if (params.len > SEV_FW_BLOB_MAX_SIZE) { if (params.len > SEV_FW_BLOB_MAX_SIZE) {
ret = -EINVAL; ret = -EINVAL;
goto e_free; goto e_free;
} }
if (!access_ok(VERIFY_WRITE, params.uaddr, params.len)) {
ret = -EFAULT;
goto e_free;
}
ret = -ENOMEM; ret = -ENOMEM;
blob = kmalloc(params.len, GFP_KERNEL); blob = kmalloc(params.len, GFP_KERNEL);
if (!blob) if (!blob)
@ -6290,13 +6288,13 @@ cmd:
goto e_free_blob; goto e_free_blob;
if (blob) { if (blob) {
if (copy_to_user((void __user *)(uintptr_t)params.uaddr, blob, params.len)) if (copy_to_user(p, blob, params.len))
ret = -EFAULT; ret = -EFAULT;
} }
done: done:
params.len = data->len; params.len = data->len;
if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params))) if (copy_to_user(measure, &params, sizeof(params)))
ret = -EFAULT; ret = -EFAULT;
e_free_blob: e_free_blob:
kfree(blob); kfree(blob);