linux-kernel - [PATCH v2] usb: ehci: Use endpoint in URB to get maxpacket

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Date:   Thu, 25 Aug 2022 01:38:13 +0600
From:   Khalid Masum <khalid.masum.92@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jack Pham <jackp@...eaurora.org>,
        Manu Gautam <mgautam@...eaurora.org>,
        Khalid Masum <khalid.masum.92@...il.com>
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 <stern@...land.harvard.edu>
Signed-off-by: Khalid Masum <khalid.masum.92@...il.com>
---
Changes since v1:
 - Update commit description
 - Use usb_endpoint_maxp() instead of checking whether getting maxpacket
   failed
 - Link: https://lore.kernel.org/lkml/20220823182758.13401-1-khalid.masum.92@gmail.com/

 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