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SubjectRe: [PATCH v2] usb:host: fix divide-by-zero in function fhci_queue_urb
Date
On Wed, 17 Apr 2019 21:49:03 +0200, Greg KH wrote:
> On Wed, Apr 17, 2019 at 05:05:33PM +0000, zhuyan (M) wrote:
> > On Wed, 17 Apr 2019, Alan Stern wrote:
> >
> > > On Wed, 17 Apr 2019, zhuyan (M) wrote:
> > >
> > > > On Tue, 16 Apr 2019 11:07:56 -0400, Alan Stern wrote:
> > > >
> > > > > On Tue, 16 Apr 2019, zhuyan (M) wrote:
> > > > > > On Tue, 16 Apr 2019 at 11:45:45 +0200, Greg KH wrote:
> > > > > > > On Tue, Apr 09, 2019 at 10:37:12PM +0800, zhuyan wrote:
> > > > > > > > In function fhci_queue_urb, the divisor of expression
> > > > > > > > (urb->transfer_buffer_length % usb_maxpacket(urb->dev,
> > > > > > > > urb->pipe,
> > > > > > > > usb_pipeout(urb->pipe))) may be zero.
> > > > > > >
> > > > > > > How can you hit that?
> > > > > > >
> > > > > > > > When it is zero, unexpected results may occur, so it is
> > > > > > > > necessary to ensure that the divisor is not zero.
> > > > > > > >
> > > > > > > > Signed-off-by: zhuyan <zhuyan34@huawei.com>
> > > > > > >
> > > > > > > I need a "Full" name here, not just a single name. Whatever you use to sign documents is good.
> > > > > > >
> > > > > > > thanks,
> > > > > > >
> > > > > > > greg k-h
> > > > > >
> > > > > > In function usb_maxpacket, when ep is NULL, its return value is 0.
> > > > >
> > > > > fhci_queue_urb() shouldn't use urb->pipe to compute the
> > > > > maxpacket size anyway. It should use usb_endpoint_maxp(&urb->ep->desc).
> > > >
> > > > Currently, fhci_queue_urb(), call usb_maxpacket() multiple times
> > > > to calculate the maxpacket size. The usb_maxpacket() will call
> > > > usb_endpoint_maxp() to compute the maxpacket size.
> > >
> > > I know that. What fhci_queue_urb() is doing is wrong. You should change it:
> > > Make it call usb_endpoint_maxp directly instead of calling usb_maxpacket.
> > >
> >
> > >From 1996456d0cc17b5ff7746a598ff355b25d13db3e Mon Sep 17 00:00:00
> > >2001
> > From: zhuyan <zhuyan34@huawei.com>
> > Date: Thu, 18 Apr 2019 00:53:03 +0800
> > Subject: [PATCH] usb: host: fix divide-by-zero in function
> > fhci_queue_urb
> >
> > fhci_queue_urb() shouldn't use urb->pipe to compute the maxpacket size
> > anyway.It should use usb_endpoint_maxp(&urb->ep->desc).
> >
> > In function fhci_queue_urb, the divisor of expression
> > (urb->transfer_buffer_length % usb_maxpacket(urb->dev, urb->pipe,
> > usb_pipeout(urb->pipe))) may be zero. When it is zero, unexpected
> > results may occur, so it is necessary to ensure that the divisor is not zero.
> >
> > Signed-off-by: zhuyan <zhuyan34@huawei.com>
>
> I still need a full name here and on the From: line :(

I am so sorry. I will change it.

From 1996456d0cc17b5ff7746a598ff355b25d13db3e Mon Sep 17 00:00:00 2001
From: Yan Zhu <zhuyan34@huawei.com>
Date: Thu, 18 Apr 2019 00:53:03 +0800
Subject: [PATCH] usb: host: fix divide-by-zero in function fhci_queue_urb

fhci_queue_urb() shouldn't use urb->pipe to compute the maxpacket
size anyway.It should use usb_endpoint_maxp(&urb->ep->desc).

In function fhci_queue_urb, the divisor of expression
(urb->transfer_buffer_length % usb_maxpacket(urb->dev, urb->pipe,
usb_pipeout(urb->pipe))) may be zero. When it is zero, unexpected results
may occur, so it is necessary to ensure that the divisor is not zero.

Signed-off-by: Yan Zhu <zhuyan34@huawei.com>
---
drivers/usb/host/fhci-sched.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/host/fhci-sched.c b/drivers/usb/host/fhci-sched.c
index 3d12cdd..7dcfe22 100644
--- a/drivers/usb/host/fhci-sched.c
+++ b/drivers/usb/host/fhci-sched.c
@@ -704,6 +704,7 @@ void fhci_queue_urb(struct fhci_hcd *fhci, struct urb *urb)
struct td *td;
u8 *data;
u16 cnt = 0;
+ u16 max_pkt_size = 0;

if (ed == NULL) {
ed = fhci_get_empty_ed(fhci);
@@ -727,8 +728,7 @@ void fhci_queue_urb(struct fhci_hcd *fhci, struct urb *urb)
}
ed->speed = (urb->dev->speed == USB_SPEED_LOW) ?
FHCI_LOW_SPEED : FHCI_FULL_SPEED;
- ed->max_pkt_size = usb_maxpacket(urb->dev,
- urb->pipe, usb_pipeout(urb->pipe));
+ ed->max_pkt_size = usb_endpoint_maxp(&urb->ep->desc);
urb->ep->hcpriv = ed;
fhci_dbg(fhci, "new ep speed=%d max_pkt_size=%d\n",
ed->speed, ed->max_pkt_size);
@@ -765,11 +765,12 @@ void fhci_queue_urb(struct fhci_hcd *fhci, struct urb *urb)

switch (ed->mode) {
case FHCI_TF_BULK:
+ max_pkt_size = usb_endpoint_maxp(&urb->ep->desc);
if (urb->transfer_flags & URB_ZERO_PACKET &&
urb->transfer_buffer_length > 0 &&
+ (max_pkt_size != 0) &&
((urb->transfer_buffer_length %
- usb_maxpacket(urb->dev, urb->pipe,
- usb_pipeout(urb->pipe))) == 0))
+ max_pkt_size) == 0))
urb_state = US_BULK0;
while (data_len > 4096) {
td = fhci_td_fill(fhci, urb, urb_priv, ed, cnt,
@@ -807,8 +808,8 @@ void fhci_queue_urb(struct fhci_hcd *fhci, struct urb *urb)
break;
case FHCI_TF_CTRL:
ed->dev_addr = usb_pipedevice(urb->pipe);
- ed->max_pkt_size = usb_maxpacket(urb->dev, urb->pipe,
- usb_pipeout(urb->pipe));
+ ed->max_pkt_size = usb_endpoint_maxp(&urb->ep->desc);
+
/* setup stage */
td = fhci_td_fill(fhci, urb, urb_priv, ed, cnt++, FHCI_TA_SETUP,
USB_TD_TOGGLE_DATA0, urb->setup_packet, 8, 0, 0, true);
--
1.8.5.6



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