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Date:   Tue, 7 May 2019 12:20:12 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Colin King <colin.king@canonical.com>
Cc:     Vladimir Oltean <olteanv@gmail.com>, Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
        netdev@vger.kernel.org
Subject: Re: [PATCH][next] net: dsa: sja1105: fix comparisons against
 uninitialized status fields
Message-ID: <20190507092012.GL2269@kadam>
References: <20190507084458.22520-1-colin.king@canonical.com>
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On Tue, May 07, 2019 at 09:44:58AM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The call to sja1105_status_get to set various fields in the status
> structure can potentially be skipped in a while-loop because of a couple
> of prior continuation jump paths. This can potientially lead to checking
> be checking against an uninitialized fields in the structure which may
> lead to unexpected results.  Fix this by ensuring all the fields in status
> are initialized to zero to be safe.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: 8aa9ebccae87 ("net: dsa: Introduce driver for NXP SJA1105 5-port L2 switch")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/net/dsa/sja1105/sja1105_spi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
> index 244a94ccfc18..76f6a51e10d9 100644
> --- a/drivers/net/dsa/sja1105/sja1105_spi.c
> +++ b/drivers/net/dsa/sja1105/sja1105_spi.c
> @@ -394,7 +394,7 @@ int sja1105_static_config_upload(struct sja1105_private *priv)
>  	struct sja1105_static_config *config = &priv->static_config;
>  	const struct sja1105_regs *regs = priv->info->regs;
>  	struct device *dev = &priv->spidev->dev;
> -	struct sja1105_status status;
> +	struct sja1105_status status = {};

The exit condition isn't right.  It should continue if ret is negative
or the CRC stuff is invalid but right now it's ignoring ret.  It would
be better could just add a break statement at the very end and remove
the status checks.  Like so:

diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
index 244a94ccfc18..3af3b0f3cc44 100644
--- a/drivers/net/dsa/sja1105/sja1105_spi.c
+++ b/drivers/net/dsa/sja1105/sja1105_spi.c
@@ -466,8 +466,9 @@ int sja1105_static_config_upload(struct sja1105_private *priv)
 				"invalid, retrying...\n");
 			continue;
 		}
-	} while (--retries && (status.crcchkl == 1 || status.crcchkg == 1 ||
-		 status.configs == 0 || status.ids == 1));
+		/* Success! */
+		break;
+	} while (--retries);
 
 	if (!retries) {
 		rc = -EIO;