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Date: Mon, 19 Jul 2021 16:49:06 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Pavel Skripkin <paskripkin@...il.com>, Marc Kleine-Budde <mkl@...gutronix.de> Subject: [PATCH 4.9 004/245] net: can: ems_usb: fix use-after-free in ems_usb_disconnect() From: Pavel Skripkin <paskripkin@...il.com> commit ab4a0b8fcb9a95c02909b62049811bd2e586aaa4 upstream. In ems_usb_disconnect() dev pointer, which is netdev private data, is used after free_candev() call: | if (dev) { | unregister_netdev(dev->netdev); | free_candev(dev->netdev); | | unlink_all_urbs(dev); | | usb_free_urb(dev->intr_urb); | | kfree(dev->intr_in_buffer); | kfree(dev->tx_msg_buffer); | } Fix it by simply moving free_candev() at the end of the block. Fail log: | BUG: KASAN: use-after-free in ems_usb_disconnect | Read of size 8 at addr ffff88804e041008 by task kworker/1:2/2895 | | CPU: 1 PID: 2895 Comm: kworker/1:2 Not tainted 5.13.0-rc5+ #164 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.4 | Workqueue: usb_hub_wq hub_event | Call Trace: | dump_stack (lib/dump_stack.c:122) | print_address_description.constprop.0.cold (mm/kasan/report.c:234) | kasan_report.cold (mm/kasan/report.c:420 mm/kasan/report.c:436) | ems_usb_disconnect (drivers/net/can/usb/ems_usb.c:683 drivers/net/can/usb/ems_usb.c:1058) Fixes: 702171adeed3 ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface") Link: https://lore.kernel.org/r/20210617185130.5834-1-paskripkin@gmail.com Cc: linux-stable <stable@...r.kernel.org> Signed-off-by: Pavel Skripkin <paskripkin@...il.com> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/net/can/usb/ems_usb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/net/can/usb/ems_usb.c +++ b/drivers/net/can/usb/ems_usb.c @@ -1064,7 +1064,6 @@ static void ems_usb_disconnect(struct us if (dev) { unregister_netdev(dev->netdev); - free_candev(dev->netdev); unlink_all_urbs(dev); @@ -1072,6 +1071,8 @@ static void ems_usb_disconnect(struct us kfree(dev->intr_in_buffer); kfree(dev->tx_msg_buffer); + + free_candev(dev->netdev); } }
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