Re: [PATCH] net: usb: asix: init MAC address buffers

[Dan Williams <dcbw@redhat.com>]

On Mon, 2019-07-01 at 06:45 +0700, Phong Tran wrote:
> This is for fixing bug KMSAN: uninit-value in ax88772_bind
> 
> Tested by
> https://groups.google.com/d/msg/syzkaller-bugs/aFQurGotng4/cFe9nxMCCwAJ
> 
> Reported-by: syzbot+8a3fc6674bbc3978ed4e@syzkaller.appspotmail.com
> 
> syzbot found the following crash on:
> 
> HEAD commit:    f75e4cfe kmsan: use kmsan_handle_urb() in urb.c
> git tree:       kmsan
> console output: 
> https://syzkaller.appspot.com/x/log.txt?x=136d720ea00000
> kernel config:
> https://syzkaller.appspot.com/x/.config?x=602468164ccdc30a
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=8a3fc6674bbc3978ed4e
> compiler:       clang version 9.0.0 (/home/glider/llvm/clang
> 06d00afa61eef8f7f501ebdb4e8612ea43ec2d78)
> syz repro:
> https://syzkaller.appspot.com/x/repro.syz?x=12788316a00000
> C reproducer:   
> https://syzkaller.appspot.com/x/repro.c?x=120359aaa00000
> 
> ==================================================================
> BUG: KMSAN: uninit-value in is_valid_ether_addr
> include/linux/etherdevice.h:200 [inline]
> BUG: KMSAN: uninit-value in asix_set_netdev_dev_addr
> drivers/net/usb/asix_devices.c:73 [inline]
> BUG: KMSAN: uninit-value in ax88772_bind+0x93d/0x11e0
> drivers/net/usb/asix_devices.c:724
> CPU: 0 PID: 3348 Comm: kworker/0:2 Not tainted 5.1.0+ #1
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
>   kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
>   __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
>   is_valid_ether_addr include/linux/etherdevice.h:200 [inline]
>   asix_set_netdev_dev_addr drivers/net/usb/asix_devices.c:73 [inline]
>   ax88772_bind+0x93d/0x11e0 drivers/net/usb/asix_devices.c:724
>   usbnet_probe+0x10f5/0x3940 drivers/net/usb/usbnet.c:1728
>   usb_probe_interface+0xd66/0x1320 drivers/usb/core/driver.c:361
>   really_probe+0xdae/0x1d80 drivers/base/dd.c:513
>   driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
>   __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
>   bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
>   __device_attach+0x454/0x730 drivers/base/dd.c:844
>   device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
>   bus_probe_device+0x137/0x390 drivers/base/bus.c:514
>   device_add+0x288d/0x30e0 drivers/base/core.c:2106
>   usb_set_configuration+0x30dc/0x3750 drivers/usb/core/message.c:2027
>   generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
>   usb_probe_device+0x14c/0x200 drivers/usb/core/driver.c:266
>   really_probe+0xdae/0x1d80 drivers/base/dd.c:513
>   driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
>   __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
>   bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
>   __device_attach+0x454/0x730 drivers/base/dd.c:844
>   device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
>   bus_probe_device+0x137/0x390 drivers/base/bus.c:514
>   device_add+0x288d/0x30e0 drivers/base/core.c:2106
>   usb_new_device+0x23e5/0x2ff0 drivers/usb/core/hub.c:2534
>   hub_port_connect drivers/usb/core/hub.c:5089 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
>   port_event drivers/usb/core/hub.c:5350 [inline]
>   hub_event+0x48d1/0x7290 drivers/usb/core/hub.c:5432
>   process_one_work+0x1572/0x1f00 kernel/workqueue.c:2269
>   process_scheduled_works kernel/workqueue.c:2331 [inline]
>   worker_thread+0x189c/0x2460 kernel/workqueue.c:2417
>   kthread+0x4b5/0x4f0 kernel/kthread.c:254
>   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  drivers/net/usb/asix_devices.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/usb/asix_devices.c
> b/drivers/net/usb/asix_devices.c
> index c9bc96310ed4..f514d19316b1 100644
> --- a/drivers/net/usb/asix_devices.c
> +++ b/drivers/net/usb/asix_devices.c
> @@ -230,6 +230,7 @@ static int ax88172_bind(struct usbnet *dev,
> struct usb_interface *intf)
>  	int i;
>  	unsigned long gpio_bits = dev->driver_info->data;
>  
> +	memset(buf, 0, sizeof(buf));

For array variables defined in the function itself, isn't this usually
done with:

         int ret = 0;
-        u8 buf[ETH_ALEN];
+        u8 buf[ETH_ALEN] = {0};
         int i;
         unsigned long gpio_bits = dev->driver_info->data;

eg make the compiler do it (though maybe it's smart enough to elide the
memset, I don't know). See drivers/net/ethernet/intel/igb/e1000_mac.c
for an example.

Dan

>  	usbnet_get_endpoints(dev,intf);
>  
>  	/* Toggle the GPIOs in a manufacturer/model specific way */
> @@ -681,6 +682,7 @@ static int ax88772_bind(struct usbnet *dev,
> struct usb_interface *intf)
>  	u32 phyid;
>  	struct asix_common_private *priv;
>  
> +	memset(buf, 0, sizeof(buf));
>  	usbnet_get_endpoints(dev, intf);
>  
>  	/* Maybe the boot loader passed the MAC address via device tree
> */
> @@ -1063,6 +1065,7 @@ static int ax88178_bind(struct usbnet *dev,
> struct usb_interface *intf)
>  	int ret;
>  	u8 buf[ETH_ALEN];
>  
> +	memset(buf, 0, sizeof(buf));
>  	usbnet_get_endpoints(dev,intf);
>  
>  	/* Get the MAC address */