[PATCH v4.4.y - v4.9.y] PCI/MSI: Destroy sysfs before freeing entries

[Thomas Gleixner <tglx@linutronix.de>]

Commit 3735459037114d31e5acd9894fad9aed104231a0 upstream.

free_msi_irqs() frees the MSI entries before destroying the sysfs entries
which are exposing them. Nothing prevents a concurrent free while a sysfs
file is read and accesses the possibly freed entry.

Move the sysfs release ahead of freeing the entries.

Fixes: 1c51b50c2995 ("PCI/MSI: Export MSI mode using attributes, not kobjects")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87sfw5305m.ffs@tglx
---
Backport v4.4.y and v4.9.y
---
 drivers/pci/msi.c |   24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -390,18 +390,6 @@ static void free_msi_irqs(struct pci_dev
 			for (i = 0; i < entry->nvec_used; i++)
 				BUG_ON(irq_has_action(entry->irq + i));
 
-	pci_msi_teardown_msi_irqs(dev);
-
-	list_for_each_entry_safe(entry, tmp, msi_list, list) {
-		if (entry->msi_attrib.is_msix) {
-			if (list_is_last(&entry->list, msi_list))
-				iounmap(entry->mask_base);
-		}
-
-		list_del(&entry->list);
-		kfree(entry);
-	}
-
 	if (dev->msi_irq_groups) {
 		sysfs_remove_groups(&dev->dev.kobj, dev->msi_irq_groups);
 		msi_attrs = dev->msi_irq_groups[0]->attrs;
@@ -417,6 +405,18 @@ static void free_msi_irqs(struct pci_dev
 		kfree(dev->msi_irq_groups);
 		dev->msi_irq_groups = NULL;
 	}
+
+	pci_msi_teardown_msi_irqs(dev);
+
+	list_for_each_entry_safe(entry, tmp, msi_list, list) {
+		if (entry->msi_attrib.is_msix) {
+			if (list_is_last(&entry->list, msi_list))
+				iounmap(entry->mask_base);
+		}
+
+		list_del(&entry->list);
+		free_msi_entry(entry);
+	}
 }
 
 static void pci_intx_for_msi(struct pci_dev *dev, int enable)