[PATCH v3] PCI/MSI: fix page fault when msi_populate_sysfs() failed

[Wang Hai <wanghai38@xxxxxxxxxx>]

I got a page fault report when doing fault injection test:

BUG: unable to handle page fault for address: fffffffffffffff4
...
RIP: 0010:sysfs_remove_groups+0x25/0x60
...
Call Trace:
 msi_destroy_sysfs+0x30/0xa0
 free_msi_irqs+0x11d/0x1b0
 __pci_enable_msix_range+0x67f/0x760
 pci_alloc_irq_vectors_affinity+0xe7/0x170
 vp_find_vqs_msix+0x129/0x560
 vp_find_vqs+0x52/0x230
 vp_modern_find_vqs+0x47/0xb0
 p9_virtio_probe+0xa1/0x460 [9pnet_virtio]
...
 entry_SYSCALL_64_after_hwframe+0x44/0xae

When populating msi_irqs sysfs failed (such as msi_attrs = kcalloc()
in msi_populate_sysfs() failed) in msi_capability_init() or
msix_capability_init(), dev->msi_irq_groups will point to ERR_PTR(...).
This will cause a page fault when destroying the wrong
dev->msi_irq_groups in free_msi_irqs().

msix_capability_init()/msi_capability_init()
	msi_populate_sysfs()
		msi_attrs = kcalloc() // fault injection, let msi_attrs = NULL
	free_msi_irqs()
		msi_destroy_sysfs() // msi_irq_groups is ERR_PTR(...), page fault

Define a temp variable and assign it to dev->msi_irq_groups if
the temp variable is not PTR_ERR.

Fixes: 2f170814bdd2 ("genirq/msi: Move MSI sysfs handling from PCI to MSI core")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
Acked-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
---
v2->v3: refine the commit log
v1->v2: introduce temporary variable 'groups'
 drivers/pci/msi.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 0099a00af361..4b4792940e86 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -535,6 +535,7 @@ static int msi_verify_entries(struct pci_dev *dev)
 static int msi_capability_init(struct pci_dev *dev, int nvec,
 			       struct irq_affinity *affd)
 {
+	const struct attribute_group **groups;
 	struct msi_desc *entry;
 	int ret;
 
@@ -558,12 +559,14 @@ static int msi_capability_init(struct pci_dev *dev, int nvec,
 	if (ret)
 		goto err;
 
-	dev->msi_irq_groups = msi_populate_sysfs(&dev->dev);
-	if (IS_ERR(dev->msi_irq_groups)) {
-		ret = PTR_ERR(dev->msi_irq_groups);
+	groups = msi_populate_sysfs(&dev->dev);
+	if (IS_ERR(groups)) {
+		ret = PTR_ERR(groups);
 		goto err;
 	}
 
+	dev->msi_irq_groups = groups;
+
 	/* Set MSI enabled bits	*/
 	pci_intx_for_msi(dev, 0);
 	pci_msi_set_enable(dev, 1);
@@ -691,6 +694,7 @@ static void msix_mask_all(void __iomem *base, int tsize)
 static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
 				int nvec, struct irq_affinity *affd)
 {
+	const struct attribute_group **groups;
 	void __iomem *base;
 	int ret, tsize;
 	u16 control;
@@ -730,12 +734,14 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
 
 	msix_update_entries(dev, entries);
 
-	dev->msi_irq_groups = msi_populate_sysfs(&dev->dev);
-	if (IS_ERR(dev->msi_irq_groups)) {
-		ret = PTR_ERR(dev->msi_irq_groups);
+	groups = msi_populate_sysfs(&dev->dev);
+	if (IS_ERR(groups)) {
+		ret = PTR_ERR(groups);
 		goto out_free;
 	}
 
+	dev->msi_irq_groups = groups;
+
 	/* Set MSI-X enabled bits and unmask the function */
 	pci_intx_for_msi(dev, 0);
 	dev->msix_enabled = 1;
-- 
2.17.1