[PATCH v2 3/6] KVM: SEV: Explicitly validate the dst buffer for debug operations

[Sean Christopherson]

When encrypting/decrypting guest memory, explicitly check that the
destination is non-NULL and doesn't wrap instead of subtly relying on
sev_pin_memory() to perform the check.  This will allow adding and using
a more focused single-page pinning helper.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index b9d7bd868e0b..9d2044fd910d 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1357,9 +1357,11 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 	if (copy_from_user(&debug, u64_to_user_ptr(argp->data), sizeof(debug)))
 		return -EFAULT;
 
-	if (!debug.len || debug.src_uaddr + debug.len < debug.src_uaddr)
+	if (!debug.len || !debug.src_uaddr || !debug.dst_uaddr)
 		return -EINVAL;
-	if (!debug.dst_uaddr)
+
+	if (debug.src_uaddr + debug.len < debug.src_uaddr ||
+	    debug.dst_uaddr + debug.len < debug.dst_uaddr)
 		return -EINVAL;
 
 	vaddr = debug.src_uaddr;
-- 
2.54.0.rc1.513.gad8abe7a5a-goog