Patch "PCI: Fix race condition with driver_override" has been added to the 4.4-stable tree

Patch "PCI: Fix race condition with driver_override" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    PCI: Fix race condition with driver_override

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pci-fix-race-condition-with-driver_override.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9561475db680f7144d2223a409dd3d7e322aca03 Mon Sep 17 00:00:00 2001
From: Nicolai Stange <nstange@suse.de>
Date: Mon, 11 Sep 2017 09:45:40 +0200
Subject: PCI: Fix race condition with driver_override

From: Nicolai Stange <nstange@suse.de>

commit 9561475db680f7144d2223a409dd3d7e322aca03 upstream.

The driver_override implementation is susceptible to a race condition when
different threads are reading vs. storing a different driver override.  Add
locking to avoid the race condition.

This is in close analogy to commit 6265539776a0 ("driver core: platform:
fix race condition with driver_override") from Adrian Salido.

Fixes: 782a985d7af2 ("PCI: Introduce new device binding path using pci_dev.driver_override")
Signed-off-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/pci/pci-sysfs.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -522,7 +522,7 @@ static ssize_t driver_override_store(str
 				     const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	char *driver_override, *old = pdev->driver_override, *cp;
+	char *driver_override, *old, *cp;
 
 	/* We need to keep extra room for a newline */
 	if (count >= (PAGE_SIZE - 1))
@@ -536,12 +536,15 @@ static ssize_t driver_override_store(str
 	if (cp)
 		*cp = '\0';
 
+	device_lock(dev);
+	old = pdev->driver_override;
 	if (strlen(driver_override)) {
 		pdev->driver_override = driver_override;
 	} else {
 		kfree(driver_override);
 		pdev->driver_override = NULL;
 	}
+	device_unlock(dev);
 
 	kfree(old);
 
@@ -552,8 +555,12 @@ static ssize_t driver_override_show(stru
 				    struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
+	ssize_t len;
 
-	return snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
+	device_lock(dev);
+	len = snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
+	device_unlock(dev);
+	return len;
 }
 static DEVICE_ATTR_RW(driver_override);
 


Patches currently in stable-queue which might be from nstange@suse.de are

queue-4.4/pci-fix-race-condition-with-driver_override.patch