linux-kernel - Re: [PATCH] isdn: mISDN: hfcsusb: Fix possible null-pointer dereferences in start_isoc

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Date:   Sat, 27 Jul 2019 13:29:59 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     baijiaju1990@...il.com
Cc:     isdn@...ux-pingi.de, pakki001@....edu, tranmanphong@...il.com,
        gregkh@...uxfoundation.org, rfontana@...hat.com,
        gustavo@...eddedor.com, tglx@...utronix.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] isdn: mISDN: hfcsusb: Fix possible null-pointer
 dereferences in start_isoc_chain()

From: Jia-Ju Bai <baijiaju1990@...il.com>
Date: Fri, 26 Jul 2019 16:27:36 +0800

> In start_isoc_chain(), usb_alloc_urb() on line 1392 may fail 
> and return NULL. At this time, fifo->iso[i].urb is assigned to NULL.
> 
> Then, fifo->iso[i].urb is used at some places, such as:
> LINE 1405:    fill_isoc_urb(fifo->iso[i].urb, ...)
>                   urb->number_of_packets = num_packets;
>                   urb->transfer_flags = URB_ISO_ASAP;
>                   urb->actual_length = 0;
>                   urb->interval = interval;
> LINE 1416:    fifo->iso[i].urb->...
> LINE 1419:    fifo->iso[i].urb->...
> 
> Thus, possible null-pointer dereferences may occur.
> 
> To fix these bugs, "continue" is added to avoid using fifo->iso[i].urb
> when it is NULL.
> 
> These bugs are found by a static analysis tool STCheck written by us.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>

Applied.