[PATCH 3.14 002/110] can: peak_pci: prevent use after free at netdev removal

Greg Kroah-Hartman
2014-06-28T18:55:55Z

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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
@@ -551,7 +551,7 @@ static int peak_pci_probe(struct pci_dev
{
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;
@@ -687,11 +687,13 @@ 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 */
@@ -725,10 +727,12 @@ static void peak_pci_remove(struct pci_d

/* 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 */