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From:   Qiujun Huang <hqjagain@gmail.com>
To:     johan@kernel.org, gregkh@linuxfoundation.org
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        anenbupt@gmail.com, Qiujun Huang <hqjagain@gmail.com>
Subject: [PATCH] USB: io_edgeport: fix  slab-out-of-bounds Read in edge_interrupt_callback
Date:   Wed, 25 Mar 2020 15:52:37 +0800
Message-Id: <1585122757-4528-1-git-send-email-hqjagain@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The boundary condition should be (length - 1) as we access data[position+1].

Reported-and-tested-by: syzbot+37ba33391ad5f3935bbd@syzkaller.appspotmail.com
Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
---
 drivers/usb/serial/io_edgeport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 5737add..4cca0b8 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -710,7 +710,7 @@ static void edge_interrupt_callback(struct urb *urb)
 		/* grab the txcredits for the ports if available */
 		position = 2;
 		portNumber = 0;
-		while ((position < length) &&
+		while ((position < length - 1) &&
 				(portNumber < edge_serial->serial->num_ports)) {
 			txCredits = data[position] | (data[position+1] << 8);
 			if (txCredits) {
-- 
1.8.3.1