[PATCH v5 6/6] KVM: s390: pci: Validate AIBV and AISB before pinning guest pages

[Farhan Ali <alifm@linux.ibm.com>]

The AIBV holds one bit per MSI-X vector for a given function. The size of
the bit vector is derived from the NOI and the AIBVO. If the size of the
AIBV exceeds a single page boundary, then reject the request as we cannot
safely pin the guest AIBV.

Similarly reject the request if the AISB address is not 8-byte aligned as
the architecture requires doubleword alignment for the summary bit address.
Since the AISBO can address up to 64 bits, the size of the AISB can only be
8 bytes for the function. This also ensures the AISB doesn't exceed a
single page boundary.

Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding")
Cc: stable@vger.kernel.org
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
 arch/s390/kvm/pci.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index ca8ef76bcf6b..25185d04ca28 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -244,7 +244,7 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
 				   bool assist)
 {
 	struct page *pages[1], *aibv_page, *aisb_page = NULL;
-	unsigned int msi_vecs, idx;
+	unsigned int msi_vecs, idx, size;
 	struct zpci_gaite *gaite;
 	unsigned long hva, bit;
 	struct kvm *kvm;
@@ -271,6 +271,15 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
 		return gisc;
 
 	/* Replace AIBV address */
+	size = BITS_TO_LONGS(msi_vecs) * sizeof(unsigned long);
+	size += (fib->fmt0.aibvo / 8);
+	npages = DIV_ROUND_UP((fib->fmt0.aibv & ~PAGE_MASK) + size, PAGE_SIZE);
+	/* AIBV cannot span more than 1 page */
+	if (npages > 1) {
+		rc = -EINVAL;
+		goto out;
+	}
+
 	idx = srcu_read_lock(&kvm->srcu);
 	hva = gfn_to_hva(kvm, gpa_to_gfn((gpa_t)fib->fmt0.aibv));
 	npages = pin_user_pages_fast(hva, 1, FOLL_WRITE | FOLL_LONGTERM, pages);
@@ -286,6 +295,12 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
 
 	/* Pin the guest AISB if one was specified */
 	if (fib->fmt0.sum == 1) {
+		/* AISB must be dword aligned */
+		if (fib->fmt0.aisb & 0x7) {
+			rc = -EINVAL;
+			goto unpin1;
+		}
+
 		idx = srcu_read_lock(&kvm->srcu);
 		hva = gfn_to_hva(kvm, gpa_to_gfn((gpa_t)fib->fmt0.aisb));
 		npages = pin_user_pages_fast(hva, 1, FOLL_WRITE | FOLL_LONGTERM,
-- 
2.43.0