2022-08-24 20:10:38

by Khalid Masum

Subject: [PATCH v2] usb: ehci: Use endpoint in URB to get maxpacket

usb_maxpacket() looks up the endpoint number in the pipe which can fail
if the interface or configuration changes before the routine is called.
This is unexpected and may even cause a modulo by zero afterwards.

So use usb_endpoint_maxp() routine which uses the endpoint stored in URB
to get the maxpacket.

Addresses-Coverity: 744857 ("Division or modulo by zero")
Addresses-Coverity: 1487371 ("Division or modulo by zero")
Suggested-by: Alan Stern <[email protected]>
Signed-off-by: Khalid Masum <[email protected]>
---
Changes since v1:
- Update commit description
- Use usb_endpoint_maxp() instead of checking whether getting maxpacket
failed
- Link: https://lore.kernel.org/lkml/[email protected]/

drivers/usb/host/ehci-q.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 807e64991e3e..666f5c4db25a 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -645,7 +645,7 @@ qh_urb_transaction (
token |= (1 /* "in" */ << 8);
/* else it's already initted to "out" pid (0 << 8) */

- maxpacket = usb_maxpacket(urb->dev, urb->pipe);
+ maxpacket = usb_endpoint_maxp(&urb->ep->desc);

/*
* buffer gets wrapped in one or more qtds;
@@ -1218,7 +1218,7 @@ static int ehci_submit_single_step_set_feature(

token |= (1 /* "in" */ << 8); /*This is IN stage*/

- maxpacket = usb_maxpacket(urb->dev, urb->pipe);
+ maxpacket = usb_endpoint_maxp(&urb->ep->desc);

qtd_fill(ehci, qtd, buf, len, token, maxpacket);

--
2.37.1

2022-08-25 14:42:50

by Alan Stern

Subject: Re: [PATCH v2] usb: ehci: Use endpoint in URB to get maxpacket

On Thu, Aug 25, 2022 at 01:38:13AM +0600, Khalid Masum wrote:
> usb_maxpacket() looks up the endpoint number in the pipe which can fail
> if the interface or configuration changes before the routine is called.
> This is unexpected and may even cause a modulo by zero afterwards.
>
> So use usb_endpoint_maxp() routine which uses the endpoint stored in URB
> to get the maxpacket.
>
> Addresses-Coverity: 744857 ("Division or modulo by zero")
> Addresses-Coverity: 1487371 ("Division or modulo by zero")
> Suggested-by: Alan Stern <[email protected]>
> Signed-off-by: Khalid Masum <[email protected]>
> ---
> Changes since v1:
> - Update commit description
> - Use usb_endpoint_maxp() instead of checking whether getting maxpacket
> failed
> - Link: https://lore.kernel.org/lkml/[email protected]/
>
> drivers/usb/host/ehci-q.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
> index 807e64991e3e..666f5c4db25a 100644
> --- a/drivers/usb/host/ehci-q.c
> +++ b/drivers/usb/host/ehci-q.c
> @@ -645,7 +645,7 @@ qh_urb_transaction (
> token |= (1 /* "in" */ << 8);
> /* else it's already initted to "out" pid (0 << 8) */
>
> - maxpacket = usb_maxpacket(urb->dev, urb->pipe);
> + maxpacket = usb_endpoint_maxp(&urb->ep->desc);
>
> /*
> * buffer gets wrapped in one or more qtds;
> @@ -1218,7 +1218,7 @@ static int ehci_submit_single_step_set_feature(
>
> token |= (1 /* "in" */ << 8); /*This is IN stage*/
>
> - maxpacket = usb_maxpacket(urb->dev, urb->pipe);
> + maxpacket = usb_endpoint_maxp(&urb->ep->desc);
>
> qtd_fill(ehci, qtd, buf, len, token, maxpacket);

Acked-by: Alan Stern <[email protected]>