hw/nvme: Use pcie_sriov_num_vfs()

nvme_sriov_pre_write_ctrl() used to directly inspect SR-IOV
configurations to know the number of VFs being disabled due to SR-IOV
configuration writes, but the logic was flawed and resulted in
out-of-bound memory access.

It assumed PCI_SRIOV_NUM_VF always has the number of currently enabled
VFs, but it actually doesn't in the following cases:
- PCI_SRIOV_NUM_VF has been set but PCI_SRIOV_CTRL_VFE has never been.
- PCI_SRIOV_NUM_VF was written after PCI_SRIOV_CTRL_VFE was set.
- VFs were only partially enabled because of realization failure.

It is a responsibility of pcie_sriov to interpret SR-IOV configurations
and pcie_sriov does it correctly, so use pcie_sriov_num_vfs(), which it
provides, to get the number of enabled VFs before and after SR-IOV
configuration writes.

Cc: qemu-stable@nongnu.org
Fixes: CVE-2024-26328
Fixes: 11871f5 ("hw/nvme: Add support for the Virtualization Management command")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-Id: <20240228-reuse-v8-1-282660281e60@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 91bb64a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/nvme/ctrl.c

@@ -8497,36 +8497,26 @@ static void nvme_pci_reset(DeviceState *qdev)
     nvme_ctrl_reset(n, NVME_RESET_FUNCTION);
 }
 
-static void nvme_sriov_pre_write_ctrl(PCIDevice *dev, uint32_t address,
-                                      uint32_t val, int len)
+static void nvme_sriov_post_write_config(PCIDevice *dev, uint16_t old_num_vfs)
 {
     NvmeCtrl *n = NVME(dev);
     NvmeSecCtrlEntry *sctrl;
-    uint16_t sriov_cap = dev->exp.sriov_cap;
-    uint32_t off = address - sriov_cap;
-    int i, num_vfs;
+    int i;
 
-    if (!sriov_cap) {
-        return;
-    }
-
-    if (range_covers_byte(off, len, PCI_SRIOV_CTRL)) {
-        if (!(val & PCI_SRIOV_CTRL_VFE)) {
-            num_vfs = pci_get_word(dev->config + sriov_cap + PCI_SRIOV_NUM_VF);
-            for (i = 0; i < num_vfs; i++) {
-                sctrl = &n->sec_ctrl_list.sec[i];
-                nvme_virt_set_state(n, le16_to_cpu(sctrl->scid), false);
-            }
-        }
+    for (i = pcie_sriov_num_vfs(dev); i < old_num_vfs; i++) {
+        sctrl = &n->sec_ctrl_list.sec[i];
+        nvme_virt_set_state(n, le16_to_cpu(sctrl->scid), false);
     }
 }
 
 static void nvme_pci_write_config(PCIDevice *dev, uint32_t address,
                                   uint32_t val, int len)
 {
-    nvme_sriov_pre_write_ctrl(dev, address, val, len);
+    uint16_t old_num_vfs = pcie_sriov_num_vfs(dev);
+
     pci_default_write_config(dev, address, val, len);
     pcie_cap_flr_write_config(dev, address, val, len);
+    nvme_sriov_post_write_config(dev, old_num_vfs);
 }
 
 static const VMStateDescription nvme_vmstate = {