linux-kernel - [PATCH 2/2] KVM: SVM: Fix sev_pin_memory() error checks in SEV migration utilities

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Date:   Thu,  6 May 2021 10:58:26 -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 2/2] KVM: SVM: Fix sev_pin_memory() error checks in SEV
 migration utilities

Use IS_ERR() instead of checking for a NULL pointer when querying for
sev_pin_memory() failures.  sev_pin_memory() always returns an error code
cast to a pointer, or a valid pointer; it never returns NULL.

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")
Fixes: 15fb7de1a7f5 ("KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 1f99c240db6d..9b23b7ac60fa 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1265,8 +1265,8 @@ static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	/* Pin guest memory */
 	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
 				    PAGE_SIZE, &n, 0);
-	if (!guest_page)
-		return -EFAULT;
+	if (IS_ERR(guest_page))
+		return PTR_ERR(guest_page);
 
 	/* allocate memory for header and transport buffer */
 	ret = -ENOMEM;
@@ -1457,11 +1457,12 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	data.trans_len = params.trans_len;
 
 	/* Pin guest memory */
-	ret = -EFAULT;
 	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
 				    PAGE_SIZE, &n, 0);
-	if (!guest_page)
+	if (IS_ERR(guest_page)) {
+		ret = PTR_ERR(guest_page);
 		goto e_free_trans;
+	}
 
 	/* The RECEIVE_UPDATE_DATA command requires C-bit to be always set. */
 	data.guest_address = (page_to_pfn(guest_page[0]) << PAGE_SHIFT) + offset;
-- 
2.31.1.607.g51e8a6a459-goog