[PATCH 3.2 81/92] can: peak_pci: prevent use after free at netdev removal

Ben Hutchings
2014-06-07T01:26:29Z

From: Stephane Grosjean <s.grosjean@peak-system.com>

commit 0b5a958cf4df3a5cd578b861471e62138f55c85e upstream.

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.

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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/net/can/sja1000/peak_pci.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

--- a/drivers/net/can/sja1000/peak_pci.c
+++ b/drivers/net/can/sja1000/peak_pci.c
@@ -98,7 +98,7 @@ static int __devinit peak_pci_probe(stru
{
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;
@@ -213,11 +213,13 @@ failure_remove_channels:
/* Disable interrupts */
writew(0x0, cfg_base + PITA_ICR + 2);

- 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);
}

pci_iounmap(pdev, reg_base);
@@ -247,10 +249,12 @@ static void __devexit peak_pci_remove(st

/* 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)
break;
priv = netdev_priv(dev);