Re: [RFT] lan78xx: FIX use-after-free in lan78xx_write_reg

[Andrey Konovalov]

On Wed, Sep 27, 2017 at 1:18 PM, Arvind Yadav <arvind.yadav.cs@xxxxxxxxx> wrote:
> We are not releasing 'buf' memory on failure or disconnect a device.
>
> Adding 'u8 *buf' as part of 'lan78xx_net' structure to make proper
> handle for 'buf'.
> Now releasing 'buf' memory on failure. It's allocate first in
> lan78xx_probe() and it should be freed last in lan78xx_disconnect().
>
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>

Hi Arvind,

I've tried your patch and still see a crash.

Thanks!

lan78xx 1-1:90.0 (unnamed net_device) (uninitialized): can't register MDIO bus
lan78xx: probe of 1-1:90.0 failed with error -5
usb 1-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: use-after-free in lan78xx_write_reg.isra.21+0x1a8/0x1b0
Read of size 8 at addr ffff880063dfac40 by task kworker/1:1/1152

CPU: 1 PID: 1152 Comm: kworker/1:1 Not tainted
4.14.0-rc2-42660-g24b7bd59eec0-dirty #274
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: events lan78xx_deferred_multicast_write
Call Trace:
 __dump_stack lib/dump_stack.c:16
 dump_stack+0x292/0x395 lib/dump_stack.c:52
 print_address_description+0x78/0x280 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351
 kasan_report+0x23d/0x350 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:430
 lan78xx_write_reg.isra.21+0x1a8/0x1b0 drivers/net/usb/lan78xx.c:459
 lan78xx_deferred_multicast_write+0x10d/0x1a0 drivers/net/usb/lan78xx.c:1043
 process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
 worker_thread+0x221/0x1850 kernel/workqueue.c:2253
 kthread+0x3a1/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 1848:
 save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 __kmalloc_node+0x192/0x480 mm/slub.c:3827
 kmalloc_node ./include/linux/slab.h:535
 kvmalloc_node+0x69/0xd0 mm/util.c:397
 kvmalloc ./include/linux/mm.h:529
 kvzalloc ./include/linux/mm.h:537
 alloc_netdev_mqs+0x173/0xea0 net/core/dev.c:8023
 alloc_etherdev_mqs+0x38/0x40 net/ethernet/eth.c:391
 lan78xx_probe+0x13a/0x3020 drivers/net/usb/lan78xx.c:3545
 usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
 generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
 usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
 hub_port_connect drivers/usb/core/hub.c:4903
 hub_port_connect_change drivers/usb/core/hub.c:5009
 port_event drivers/usb/core/hub.c:5115
 hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
 process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
 worker_thread+0x221/0x1850 kernel/workqueue.c:2253
 kthread+0x3a1/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Freed by task 1848:
 save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:524
 slab_free_hook mm/slub.c:1390
 slab_free_freelist_hook mm/slub.c:1412
 slab_free mm/slub.c:2988
 kfree+0xf6/0x2f0 mm/slub.c:3919
 kvfree+0x3b/0x60 mm/util.c:416
 netdev_freemem net/core/dev.c:7975
 free_netdev+0x304/0x3c0 net/core/dev.c:8137
 lan78xx_probe+0x21a4/0x3020 drivers/net/usb/lan78xx.c:3649
 usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
 generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
 usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
 hub_port_connect drivers/usb/core/hub.c:4903
 hub_port_connect_change drivers/usb/core/hub.c:5009
 port_event drivers/usb/core/hub.c:5115
 hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
 process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
 worker_thread+0x221/0x1850 kernel/workqueue.c:2253
 kthread+0x3a1/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

The buggy address belongs to the object at ffff880063dfa100
 which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 2880 bytes inside of
 8192-byte region [ffff880063dfa100, ffff880063dfc100)
The buggy address belongs to the page:
page:ffffea00018f7e00 count:1 mapcount:0 mapping:          (null)
index:0x0 compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 0000000000000000 0000000000000000 0000000100030003
raw: ffffea0001afd800 0000000300000003 ffff88006c402a80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880063dfab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880063dfab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880063dfac00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff880063dfac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff880063dfad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

> ---
>  drivers/net/usb/lan78xx.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
> index b99a7fb..e653982 100644
> --- a/drivers/net/usb/lan78xx.c
> +++ b/drivers/net/usb/lan78xx.c
> @@ -402,6 +402,7 @@ struct lan78xx_net {
>         struct statstage        stats;
>
>         struct irq_domain_data  domain_data;
> +       u8 *buf;
>  };
>
>  /* define external phy id */
> @@ -3470,6 +3471,9 @@ static void lan78xx_disconnect(struct usb_interface *intf)
>
>         usb_scuttle_anchored_urbs(&dev->deferred);
>
> +       kfree(dev->buf);
> +       dev->buf = NULL;
> +
>         lan78xx_unbind(dev, intf);
>
>         usb_kill_urb(dev->urb_intr);
> @@ -3520,7 +3524,6 @@ static int lan78xx_probe(struct usb_interface *intf,
>         int ret;
>         unsigned maxp;
>         unsigned period;
> -       u8 *buf = NULL;
>
>         udev = interface_to_usbdev(intf);
>         udev = usb_get_dev(udev);
> @@ -3588,16 +3591,15 @@ static int lan78xx_probe(struct usb_interface *intf,
>         period = dev->ep_intr->desc.bInterval;
>
>         maxp = usb_maxpacket(dev->udev, dev->pipe_intr, 0);
> -       buf = kmalloc(maxp, GFP_KERNEL);
> -       if (buf) {
> +       dev->buf = kmalloc(maxp, GFP_KERNEL);
> +       if (dev->buf) {
>                 dev->urb_intr = usb_alloc_urb(0, GFP_KERNEL);
>                 if (!dev->urb_intr) {
>                         ret = -ENOMEM;
> -                       kfree(buf);
>                         goto out3;
>                 } else {
>                         usb_fill_int_urb(dev->urb_intr, dev->udev,
> -                                        dev->pipe_intr, buf, maxp,
> +                                        dev->pipe_intr, dev->buf, maxp,
>                                          intr_complete, dev, period);
>                 }
>         }
> @@ -3626,6 +3628,8 @@ static int lan78xx_probe(struct usb_interface *intf,
>         return 0;
>
>  out3:
> +       kfree(dev->buf);
> +       dev->buf = NULL;
>         lan78xx_unbind(dev, intf);
>  out2:
>         free_netdev(netdev);
> --
> 1.9.1
>