can: peak_pci: prevent use after free at netdev removal

As remarked by Christopher R. Baker in his post at

http://marc.info/?l=linux-can&m=139707295706465&w=2

there's a possibility for an use after free condition at device removal.

This simplified patch introduces an additional variable to prevent the issue.
Thanks for catching this.

Cc: linux-stable <stable@vger.kernel.org>
Reported-by: Christopher R. Baker <cbaker@rec.ri.cmu.edu>
Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/net/can/sja1000/peak_pci.c b/drivers/net/can/sja1000/peak_pci.c
index c540e3d12e3d..564933ae218c 100644
--- a/drivers/net/can/sja1000/peak_pci.c
+++ b/drivers/net/can/sja1000/peak_pci.c
@@ -551,7 +551,7 @@ static int peak_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
         struct sja1000_priv *priv;
         struct peak_pci_chan *chan;
-        struct net_device *dev;
+        struct net_device *dev, *prev_dev;
         void __iomem *cfg_base, *reg_base;
         u16 sub_sys_id, icr;
         int i, err, channels;
@@ -688,11 +688,13 @@ failure_remove_channels:
         writew(0x0, cfg_base + PITA_ICR + 2);
 
         chan = NULL;
-        for (dev = pci_get_drvdata(pdev); dev; dev = chan->prev_dev) {
-                unregister_sja1000dev(dev);
-                free_sja1000dev(dev);
+        for (dev = pci_get_drvdata(pdev); dev; dev = prev_dev) {
                 priv = netdev_priv(dev);
                 chan = priv->priv;
+                prev_dev = chan->prev_dev;
+
+                unregister_sja1000dev(dev);
+                free_sja1000dev(dev);
         }
 
         /* free any PCIeC resources too */
@@ -726,10 +728,12 @@ static void peak_pci_remove(struct pci_dev *pdev)
 
         /* Loop over all registered devices */
         while (1) {
+                struct net_device *prev_dev = chan->prev_dev;
+
                 dev_info(&pdev->dev, "removing device %s\n", dev->name);
                 unregister_sja1000dev(dev);
                 free_sja1000dev(dev);
-                dev = chan->prev_dev;
+                dev = prev_dev;
 
                 if (!dev) {
                         /* do that only for first channel */