KVM: SVM: prevent DBG_DECRYPT and DBG_ENCRYPT overflow

This ensures that the address and length provided to DBG_DECRYPT and
DBG_ENCRYPT do not cause an overflow.

At the same time, pass the actual number of pages pinned in memory to
sev_unpin_memory() as a cleanup.

Reported-by: Cfir Cohen <cfir@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 947c35a..e0a791c 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6799,7 +6799,8 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
        struct page **src_p, **dst_p;
        struct kvm_sev_dbg debug;
        unsigned long n;
-       int ret, size;
+       unsigned int size;
+       int ret;
 
        if (!sev_guest(kvm))
                return -ENOTTY;
@@ -6807,6 +6808,11 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
        if (copy_from_user(&debug, (void __user *)(uintptr_t)argp->data, sizeof(debug)))
                return -EFAULT;
 
+       if (!debug.len || debug.src_uaddr + debug.len < debug.src_uaddr)
+               return -EINVAL;
+       if (!debug.dst_uaddr)
+               return -EINVAL;
+
        vaddr = debug.src_uaddr;
        size = debug.len;
        vaddr_end = vaddr + size;
@@ -6857,8 +6863,8 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
                                                     dst_vaddr,
                                                     len, &argp->error);
 
-               sev_unpin_memory(kvm, src_p, 1);
-               sev_unpin_memory(kvm, dst_p, 1);
+               sev_unpin_memory(kvm, src_p, n);
+               sev_unpin_memory(kvm, dst_p, n);
 
                if (ret)
                        goto err;