From 3e233385ef4a217a2812115ed84d4be36eb16817 Mon Sep 17 00:00:00 2001 From: Brijesh Singh Date: Fri, 23 Feb 2018 12:36:50 -0600 Subject: KVM: SVM: no need to call access_ok() in LAUNCH_MEASURE command MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Fixes: 0d0736f76347 (KVM: SVM: Add support for KVM_SEV_LAUNCH_MEASURE ...) Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Borislav Petkov Cc: Tom Lendacky Cc: linux-kernel@vger.kernel.org Cc: Joerg Roedel Signed-off-by: Brijesh Singh Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index b3e488a74828..ca69d53d7e6d 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -6236,16 +6236,18 @@ e_free: 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 sev_data_launch_measure *data; struct kvm_sev_launch_measure params; + void __user *p = NULL; void *blob = NULL; int ret; if (!sev_guest(kvm)) return -ENOTTY; - if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) + if (copy_from_user(¶ms, measure, sizeof(params))) return -EFAULT; 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) goto cmd; - if (params.uaddr) { + p = (void __user *)(uintptr_t)params.uaddr; + if (p) { if (params.len > SEV_FW_BLOB_MAX_SIZE) { ret = -EINVAL; goto e_free; } - if (!access_ok(VERIFY_WRITE, params.uaddr, params.len)) { - ret = -EFAULT; - goto e_free; - } - ret = -ENOMEM; blob = kmalloc(params.len, GFP_KERNEL); if (!blob) @@ -6290,13 +6288,13 @@ cmd: goto e_free_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; } done: params.len = data->len; - if (copy_to_user((void __user *)(uintptr_t)argp->data, ¶ms, sizeof(params))) + if (copy_to_user(measure, ¶ms, sizeof(params))) ret = -EFAULT; e_free_blob: kfree(blob); -- cgit v1.2.3