PCI: Fix NULL dereference in SR-IOV VF creation error path

Clean up when virtfn setup fails to prevent NULL pointer dereference
during device removal. The kernel oops below occurred due to incorrect
error handling flow when pci_setup_device() fails.

Add pci_iov_scan_device(), which handles virtfn allocation and setup and
cleans up if pci_setup_device() fails, so pci_iov_add_virtfn() doesn't need
to call pci_stop_and_remove_bus_device().  This prevents accessing
partially initialized virtfn devices during removal.

  BUG: kernel NULL pointer dereference, address: 00000000000000d0
  RIP: 0010:device_del+0x3d/0x3d0
  Call Trace:
   pci_remove_bus_device+0x7c/0x100
   pci_iov_add_virtfn+0xfa/0x200
   sriov_enable+0x208/0x420
   mlx5_core_sriov_configure+0x6a/0x160 [mlx5_core]
   sriov_numvfs_store+0xae/0x1a0

Link: https://lore.kernel.org/r/20250310084524.599225-1-shayd@nvidia.com
Fixes: e3f30d563a38 ("PCI: Make pci_destroy_dev() concurrent safe")
Signed-off-by: Shay Drory <shayd@nvidia.com>
[bhelgaas: commit log, return ERR_PTR(-ENOMEM) directly]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Keith Busch <kbusch@kernel.org>

1 files changed, 34 insertions, 14 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 121540f57d4b..10693b5d7eb6 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -285,23 +285,16 @@ const struct attribute_group sriov_vf_dev_attr_group = {
 	.is_visible = sriov_vf_attrs_are_visible,
 };
 
-int pci_iov_add_virtfn(struct pci_dev *dev, int id)
+static struct pci_dev *pci_iov_scan_device(struct pci_dev *dev, int id,
+					   struct pci_bus *bus)
 {
-	int i;
-	int rc = -ENOMEM;
-	u64 size;
-	struct pci_dev *virtfn;
-	struct resource *res;
 	struct pci_sriov *iov = dev->sriov;
-	struct pci_bus *bus;
-
-	bus = virtfn_add_bus(dev->bus, pci_iov_virtfn_bus(dev, id));
-	if (!bus)
-		goto failed;
+	struct pci_dev *virtfn;
+	int rc;
 
 	virtfn = pci_alloc_dev(bus);
 	if (!virtfn)
-		goto failed0;
+		return ERR_PTR(-ENOMEM);
 
 	virtfn->devfn = pci_iov_virtfn_devfn(dev, id);
 	virtfn->vendor = dev->vendor;
@@ -314,8 +307,35 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
 		pci_read_vf_config_common(virtfn);
 
 	rc = pci_setup_device(virtfn);
-	if (rc)
-		goto failed1;
+	if (rc) {
+		pci_dev_put(dev);
+		pci_bus_put(virtfn->bus);
+		kfree(virtfn);
+		return ERR_PTR(rc);
+	}
+
+	return virtfn;
+}
+
+int pci_iov_add_virtfn(struct pci_dev *dev, int id)
+{
+	struct pci_bus *bus;
+	struct pci_dev *virtfn;
+	struct resource *res;
+	int rc, i;
+	u64 size;
+
+	bus = virtfn_add_bus(dev->bus, pci_iov_virtfn_bus(dev, id));
+	if (!bus) {
+		rc = -ENOMEM;
+		goto failed;
+	}
+
+	virtfn = pci_iov_scan_device(dev, id, bus);
+	if (IS_ERR(virtfn)) {
+		rc = PTR_ERR(virtfn);
+		goto failed0;
+	}
 
 	virtfn->dev.parent = dev->dev.parent;
 	virtfn->multifunction = 0;