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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Jerry Ray <jerry.ray@microchip.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com, u.kleine-koenig@pengutronix.de,
        marcus.folkesson@gmail.com, lee.jones@linaro.org,
        stefan@datenfreihafen.org, bigeasy@linutronix.de,
        netdev@vger.kernel.org
Subject: [PATCH AUTOSEL 5.19 13/73] micrel: ksz8851: fixes struct pointer issue
Date:   Sun,  9 Oct 2022 18:13:51 -0400
Message-Id: <20221009221453.1216158-13-sashal@kernel.org>
In-Reply-To: <20221009221453.1216158-1-sashal@kernel.org>
References: <20221009221453.1216158-1-sashal@kernel.org>
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From: Jerry Ray <jerry.ray@microchip.com>

[ Upstream commit fef5de753ff01887cfa50990532c3890fccb9338 ]

Issue found during code review. This bug has no impact as long as the
ks8851_net structure is the first element of the ks8851_net_spi structure.
As long as the offset to the ks8851_net struct is zero, the container_of()
macro is subtracting 0 and therefore no damage done. But if the
ks8851_net_spi struct is ever modified such that the ks8851_net struct
within it is no longer the first element of the struct, then the bug would
manifest itself and cause problems.

struct ks8851_net is contained within ks8851_net_spi.
ks is contained within kss.
kss is the priv_data of the netdev structure.

Signed-off-by: Jerry Ray <jerry.ray@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/micrel/ks8851_spi.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/micrel/ks8851_spi.c b/drivers/net/ethernet/micrel/ks8851_spi.c
index 82d55fc27edc..70bc7253454f 100644
--- a/drivers/net/ethernet/micrel/ks8851_spi.c
+++ b/drivers/net/ethernet/micrel/ks8851_spi.c
@@ -413,7 +413,8 @@ static int ks8851_probe_spi(struct spi_device *spi)
 
 	spi->bits_per_word = 8;
 
-	ks = netdev_priv(netdev);
+	kss = netdev_priv(netdev);
+	ks = &kss->ks8851;
 
 	ks->lock = ks8851_lock_spi;
 	ks->unlock = ks8851_unlock_spi;
@@ -433,8 +434,6 @@ static int ks8851_probe_spi(struct spi_device *spi)
 		 IRQ_RXPSI)	/* RX process stop */
 	ks->rc_ier = STD_IRQ;
 
-	kss = to_ks8851_spi(ks);
-
 	kss->spidev = spi;
 	mutex_init(&kss->lock);
 	INIT_WORK(&kss->tx_work, ks8851_tx_work);
-- 
2.35.1