[PATCH AUTOSEL 5.2 051/123] isdn: mISDN: hfcsusb: Fix possible null-pointer dereferences in start_isoc_chain()

Sasha Levin
2019-08-14T02:12:50Z

From: Jia-Ju Bai <baijiaju1990@gmail.com>

[ Upstream commit a0d57a552b836206ad7705a1060e6e1ce5a38203 ]

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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 0e224232f7464..8fb7c5dea07fc 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;
--
2.20.1