linux-kernel - [RFC][PATCH 4/4] NFC: fdp: Fix possible buffer overflow in WCS4000 NFC driver

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Message-Id: <1513799484-12505-5-git-send-email-amit.pundir@linaro.org>
Date:   Thu, 21 Dec 2017 01:21:24 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>, linux-wireless@...r.kernel.org
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        Christophe Ricard <christophe.ricard@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        John Stultz <john.stultz@...aro.org>,
        Dmitry Shmidt <dimitrysh@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: [RFC][PATCH 4/4] NFC: fdp: Fix possible buffer overflow in WCS4000 NFC driver

From: Suren Baghdasaryan <surenb@...gle.com>

Possible buffer overflow when reading next_read_size bytes into
tmp buffer after next_read_size was extracted from a previous packet.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
---
 drivers/nfc/fdp/i2c.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/nfc/fdp/i2c.c b/drivers/nfc/fdp/i2c.c
index c4da50e07bbc..08a4f82a2965 100644
--- a/drivers/nfc/fdp/i2c.c
+++ b/drivers/nfc/fdp/i2c.c
@@ -176,6 +176,16 @@ static int fdp_nci_i2c_read(struct fdp_i2c_phy *phy, struct sk_buff **skb)
 		/* Packet that contains a length */
 		if (tmp[0] == 0 && tmp[1] == 0) {
 			phy->next_read_size = (tmp[2] << 8) + tmp[3] + 3;
+			/*
+			 * Ensure next_read_size does not exceed sizeof(tmp)
+			 * for reading that many bytes during next iteration
+			 */
+			if (phy->next_read_size > FDP_NCI_I2C_MAX_PAYLOAD) {
+				dev_dbg(&client->dev, "%s: corrupted packet\n",
+					__func__);
+				phy->next_read_size = 5;
+				goto flush;
+			}
 		} else {
 			phy->next_read_size = FDP_NCI_I2C_MIN_PAYLOAD;
 
-- 
2.7.4