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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dan Carpenter <dan.carpenter@oracle.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 315/348] staging: gdm724x: check for overflow in gdm_lte_netif_rx()
Date:   Mon, 12 Jul 2021 08:11:39 +0200
Message-Id: <20210712060745.796201484@linuxfoundation.org>
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From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 7002b526f4ff1f6da34356e67085caafa6be383a ]

This code assumes that "len" is at least 62 bytes, but we need a check
to prevent a read overflow.

Fixes: 61e121047645 ("staging: gdm7240: adding LTE USB driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YMcoTPsCYlhh2TQo@mwanda
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/staging/gdm724x/gdm_lte.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/gdm724x/gdm_lte.c b/drivers/staging/gdm724x/gdm_lte.c
index 182a77de2d04..8093d0608638 100644
--- a/drivers/staging/gdm724x/gdm_lte.c
+++ b/drivers/staging/gdm724x/gdm_lte.c
@@ -611,10 +611,12 @@ static void gdm_lte_netif_rx(struct net_device *dev, char *buf,
 						  * bytes (99,130,83,99 dec)
 						  */
 			} __packed;
-			void *addr = buf + sizeof(struct iphdr) +
-				sizeof(struct udphdr) +
-				offsetof(struct dhcp_packet, chaddr);
-			ether_addr_copy(nic->dest_mac_addr, addr);
+			int offset = sizeof(struct iphdr) +
+				     sizeof(struct udphdr) +
+				     offsetof(struct dhcp_packet, chaddr);
+			if (offset + ETH_ALEN > len)
+				return;
+			ether_addr_copy(nic->dest_mac_addr, buf + offset);
 		}
 	}
 
-- 
2.30.2