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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, Colin Ian King <colin.king@canonical.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 061/144] 6lowpan: iphc: Fix an off-by-one check of array index
Date:   Mon, 13 Sep 2021 15:14:02 +0200
Message-Id: <20210913131050.011719736@linuxfoundation.org>
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From: Colin Ian King <colin.king@canonical.com>

[ Upstream commit 9af417610b6142e826fd1ee8ba7ff3e9a2133a5a ]

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@canonical.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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);
 
-- 
2.30.2