Subject: Re: [PATCH 5/5] ath9k: Fix general protection fault in ath9k_hif_usb_rx_cb

From: Dan Carpenter <[email-masked]>
Date: Tue, 7 Apr 2020 15:50:10 +0300

On Sat, Apr 04, 2020 at 12:18:38PM +0800, Qiujun Huang wrote:
> In ath9k_hif_usb_rx_cb interface number is assumed to be 0.
> usb_ifnum_to_if(urb->dev, 0)
> But it isn't always true.
> 
> The case reported by syzbot:
> https://lore.kernel.org/linux-usb/[email-masked]
> usb 2-1: new high-speed USB device number 2 using dummy_hcd
> usb 2-1: config 1 has an invalid interface number: 2 but max is 0
> usb 2-1: config 1 has no interface number 0
> usb 2-1: New USB device found, idVendor=0cf3, idProduct=9271, bcdDevice=
> 1.08
> usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> general protection fault, probably for non-canonical address
> 0xdffffc0000000015: 0000 [#1] SMP KASAN
> KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc5-syzkaller #0
> 
> Call Trace
> __usb_hcd_giveback_urb+0x29a/0x550 drivers/usb/core/hcd.c:1650
> usb_hcd_giveback_urb+0x368/0x420 drivers/usb/core/hcd.c:1716
> dummy_timer+0x1258/0x32ae drivers/usb/gadget/udc/dummy_hcd.c:1966
> call_timer_fn+0x195/0x6f0 kernel/time/timer.c:1404
> expire_timers kernel/time/timer.c:1449 [inline]
> __run_timers kernel/time/timer.c:1773 [inline]
> __run_timers kernel/time/timer.c:1740 [inline]
> run_timer_softirq+0x5f9/0x1500 kernel/time/timer.c:1786
> __do_softirq+0x21e/0x950 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:373 [inline]
> irq_exit+0x178/0x1a0 kernel/softirq.c:413
> exiting_irq arch/x86/include/asm/apic.h:546 [inline]
> smp_apic_timer_interrupt+0x141/0x540 arch/x86/kernel/apic/apic.c:1146
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
> 
> Reported-and-tested-by: [email-masked]
> Signed-off-by: Qiujun Huang <[email-masked]>
> ---
>  drivers/net/wireless/ath/ath9k/hif_usb.c | 48 ++++++++++++++++++------
>  drivers/net/wireless/ath/ath9k/hif_usb.h |  5 +++
>  2 files changed, 42 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
> index 6049d3766c64..4ed21dad6a8e 100644
> --- a/drivers/net/wireless/ath/ath9k/hif_usb.c
> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
> @@ -643,9 +643,9 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
>  
>  static void ath9k_hif_usb_rx_cb(struct urb *urb)
>  {
> -	struct sk_buff *skb = (struct sk_buff *) urb->context;
> -	struct hif_device_usb *hif_dev =
> -		usb_get_intfdata(usb_ifnum_to_if(urb->dev, 0));
> +	struct rx_buf *rx_buf = (struct rx_buf *)urb->context;
> +	struct hif_device_usb *hif_dev = rx_buf->hif_dev;
> +	struct sk_buff *skb = rx_buf->skb;
>  	int ret;
>  
>  	if (!skb)

This "if (!skb)" error path returns directly and leaks "rx_buf".
Of course, it's an impossible condition.  We should just delete the
check.

> @@ -685,14 +685,15 @@ static void ath9k_hif_usb_rx_cb(struct urb *urb)
>  	return;
>  free:
>  	kfree_skb(skb);
> +	kfree(rx_buf);
>  }
>  
>  static void ath9k_hif_usb_reg_in_cb(struct urb *urb)
>  {
> -	struct sk_buff *skb = (struct sk_buff *) urb->context;
> +	struct rx_buf *rx_buf = (struct rx_buf *)urb->context;
> +	struct hif_device_usb *hif_dev = rx_buf->hif_dev;
> +	struct sk_buff *skb = rx_buf->skb;
>  	struct sk_buff *nskb;
> -	struct hif_device_usb *hif_dev =
> -		usb_get_intfdata(usb_ifnum_to_if(urb->dev, 0));
>  	int ret;
>  
>  	if (!skb)

Same.

> @@ -750,6 +751,7 @@ static void ath9k_hif_usb_reg_in_cb(struct urb *urb)
>  	return;
>  free:
>  	kfree_skb(skb);
> +	kfree(rx_buf);
>  	urb->context = NULL;
>  }
>  

regards,
dan carpenter