Patchwork usb:host: fix divide-by-zero in function fhci_queue_urb

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Submitter zhuyan
Date April 9, 2019, 2:37 p.m.
Message ID <1554820632-13782-1-git-send-email-zhuyan34@huawei.com>
Download mbox | patch
Permalink /patch/768647/
State New
Headers show

Comments

zhuyan - April 9, 2019, 2:37 p.m.
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>
---
 drivers/usb/host/fhci-sched.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
Greg Kroah-Hartman - April 16, 2019, 9:45 a.m.
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

Patch

diff --git a/drivers/usb/host/fhci-sched.c b/drivers/usb/host/fhci-sched.c
index 3d12cdd..27ed63c 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);
@@ -765,11 +766,13 @@  void fhci_queue_urb(struct fhci_hcd *fhci, struct urb *urb)
 
 	switch (ed->mode) {
 	case FHCI_TF_BULK:
+		max_pkt_size = usb_maxpacket(urb->dev, urb->pipe,
+					usb_pipeout(urb->pipe));
 		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,