2019-07-26 08:29:14

by Jia-Ju Bai

Subject: [PATCH] isdn: mISDN: hfcsusb: Fix possible null-pointer dereferences in start_isoc_chain()

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 <[email protected]>
---
drivers/isdn/hardware/mISDN/hfcsusb.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
index 0e224232f746..8fb7c5dea07f 100644
--- a/drivers/isdn/hardware/mISDN/hfcsusb.c
+++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
@@ -1394,6 +1394,7 @@ start_isoc_chain(struct usb_fifo *fifo, int num_packets_per_urb,
printk(KERN_DEBUG
"%s: %s: alloc urb for fifo %i failed",
hw->name, __func__, fifo->fifonum);
+ continue;
}
fifo->iso[i].owner_fifo = (struct usb_fifo *) fifo;
fifo->iso[i].indx = i;
--
2.17.0

2019-07-27 20:30:59

by David Miller

Subject: Re: [PATCH] isdn: mISDN: hfcsusb: Fix possible null-pointer dereferences in start_isoc_chain()

From: Jia-Ju Bai <[email protected]>
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 <[email protected]>

Applied.