[PATCH 4.19 14/37] can: peak_pci: peak_pci_remove(): fix UAF

Greg Kroah-Hartman
2021-10-25T19:28:45Z

From: Zheyu Ma <zheyuma97@gmail.com>

commit 949fe9b35570361bc6ee2652f89a0561b26eec98 upstream.

When remove the module peek_pci, referencing 'chan' again after
releasing 'dev' will cause UAF.

Fix this by releasing 'dev' later.

The following log reveals it:

[ 35.961814 ] BUG: KASAN: use-after-free in peak_pci_remove+0x16f/0x270 [peak_pci]
[ 35.963414 ] Read of size 8 at addr ffff888136998ee8 by task modprobe/5537
[ 35.965513 ] Call Trace:
[ 35.965718 ] dump_stack_lvl+0xa8/0xd1
[ 35.966028 ] print_address_description+0x87/0x3b0
[ 35.966420 ] kasan_report+0x172/0x1c0
[ 35.966725 ] ? peak_pci_remove+0x16f/0x270 [peak_pci]
[ 35.967137 ] ? trace_irq_enable_rcuidle+0x10/0x170
[ 35.967529 ] ? peak_pci_remove+0x16f/0x270 [peak_pci]
[ 35.967945 ] __asan_report_load8_noabort+0x14/0x20
[ 35.968346 ] peak_pci_remove+0x16f/0x270 [peak_pci]
[ 35.968752 ] pci_device_remove+0xa9/0x250

Fixes: e6d9c80b7ca1 ("can: peak_pci: add support of some new PEAK-System PCI cards")
Link: https://lore.kernel.org/all/1634192913-15639-1-git-send-email-zheyuma97@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Zheyu Ma <zheyuma97@gmail.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 | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

--- a/drivers/net/can/sja1000/peak_pci.c
+++ b/drivers/net/can/sja1000/peak_pci.c
@@ -739,16 +739,15 @@ static void peak_pci_remove(struct pci_d
struct net_device *prev_dev = chan->prev_dev;

dev_info(&pdev->dev, "removing device %s\n", dev->name);
+ /* do that only for first channel */
+ if (!prev_dev && chan->pciec_card)
+ peak_pciec_remove(chan->pciec_card);
unregister_sja1000dev(dev);
free_sja1000dev(dev);
dev = prev_dev;

- if (!dev) {
- /* do that only for first channel */
- if (chan->pciec_card)
- peak_pciec_remove(chan->pciec_card);
+ if (!dev)
break;
- }
priv = netdev_priv(dev);
chan = priv->priv;
}