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From:   Khalid Masum <khalid.masum.92@gmail.com>
To:     Alan Stern <stern@rowland.harvard.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Khalid Masum <khalid.masum.92@gmail.com>
Subject: [PATCH 1/2] usb: ehci: Prevent possible modulo by zero
Date:   Wed, 24 Aug 2022 00:27:57 +0600
Message-Id: <20220823182758.13401-2-khalid.masum.92@gmail.com>
In-Reply-To: <20220823182758.13401-1-khalid.masum.92@gmail.com>
References: <20220823182758.13401-1-khalid.masum.92@gmail.com>
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usb_maxpacket() returns 0 if it fails to fetch the endpoint. This
value is later used for calculating modulo. Which can cause modulo
by zero in qtd_fill and qh_urb_transaction.

Prevent this breakage by returning if maxpacket is found to be 0.

Fixes coverity warning: 744857 ("Division or modulo by zero")
Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
---
 drivers/usb/host/ehci-q.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 807e64991e3e..eb31d13e9ecd 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -646,6 +646,8 @@ qh_urb_transaction (
 	/* else it's already initted to "out" pid (0 << 8) */
 
 	maxpacket = usb_maxpacket(urb->dev, urb->pipe);
+	if (unlikely(!maxpacket))
+		return NULL;
 
 	/*
 	 * buffer gets wrapped in one or more qtds;
-- 
2.37.1