linux-kernel - [PATCH 1/2] KVM: SVM: Return -EFAULT if copy_to

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Message-Id: <20210506175826.2166383-2-seanjc@google.com>
Date:   Thu,  6 May 2021 10:58:25 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ashish Kalra <ashish.kalra@....com>
Subject: [PATCH 1/2] KVM: SVM: Return -EFAULT if copy_to_user() for SEV mig
 packet header fails

Return -EFAULT if copy_to_user() fails; if accessing user memory faults,
copy_to_user() returns the number of bytes remaining, not an error code.

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Steve Rutherford <srutherford@...gle.com>
Cc: Brijesh Singh <brijesh.singh@....com>
Cc: Ashish Kalra <ashish.kalra@....com>
Fixes: d3d1af85e2c7 ("KVM: SVM: Add KVM_SEND_UPDATE_DATA command")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a9d8d6aafdb8..1f99c240db6d 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1303,8 +1303,9 @@ static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	}
 
 	/* Copy packet header to userspace. */
-	ret = copy_to_user((void __user *)(uintptr_t)params.hdr_uaddr, hdr,
-				params.hdr_len);
+	if (copy_to_user((void __user *)(uintptr_t)params.hdr_uaddr, hdr,
+			 params.hdr_len))
+		ret = -EFAULT;
 
 e_free_trans_data:
 	kfree(trans_data);
-- 
2.31.1.607.g51e8a6a459-goog