netdev - [PATCH] 6lowpan: iphc: Fix an off-by-one check of array index

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Message-Id: <20210712121440.17860-1-colin.king@canonical.com>
Date:   Mon, 12 Jul 2021 13:14:40 +0100
From:   Colin King <colin.king@...onical.com>
To:     Alexander Aring <alex.aring@...il.com>,
        Jukka Rissanen <jukka.rissanen@...ux.intel.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Schmidt <stefan@....samsung.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        linux-bluetooth@...r.kernel.org, linux-wpan@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] 6lowpan: iphc: Fix an off-by-one check of array index

From: Colin Ian King <colin.king@...onical.com>

The bounds check of id is off-by-one and the comparison should
be >= rather >. Currently the WARN_ON_ONCE check does not stop
the out of range indexing of &ldev->ctx.table[id] so also add
a return path if the bounds are out of range.

Addresses-Coverity: ("Illegal address computation").
Fixes: 5609c185f24d ("6lowpan: iphc: add support for stateful compression")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/6lowpan/debugfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/6lowpan/debugfs.c b/net/6lowpan/debugfs.c
index 1c140af06d52..600b9563bfc5 100644
--- a/net/6lowpan/debugfs.c
+++ b/net/6lowpan/debugfs.c
@@ -170,7 +170,8 @@ static void lowpan_dev_debugfs_ctx_init(struct net_device *dev,
 	struct dentry *root;
 	char buf[32];
 
-	WARN_ON_ONCE(id > LOWPAN_IPHC_CTX_TABLE_SIZE);
+	if (WARN_ON_ONCE(id >= LOWPAN_IPHC_CTX_TABLE_SIZE))
+		return;
 
 	sprintf(buf, "%d", id);
 
-- 
2.31.1