linux-kernel - Re: [PATCH] octeontx2-af: Fix uninitialized scalar variable

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Message-ID: <Z6rk3Z6TuFSJgSaV@mev-dev.igk.intel.com>
Date: Tue, 11 Feb 2025 06:50:56 +0100
From: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
To: Ethan Carter Edwards <ethan@...ancedwards.com>
Cc: hariprasad <hkelam@...vell.com>, Sunil Goutham <sgoutham@...vell.com>,
	Geetha sowjanya <gakula@...vell.com>,
	Subbaraya Sundeep <sbhatta@...vell.com>,
	Bharat Bhushan <bbhushan2@...vell.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] octeontx2-af: Fix uninitialized scalar variable

On Mon, Feb 10, 2025 at 09:01:52PM -0500, Ethan Carter Edwards wrote:
> The variable *max_mtu* is uninitialized in the function
> otx2_get_max_mtu. It is only assigned in the if-statement, leaving the
> possibility of returning an uninitialized value.

In which case? If rc == 0 at the end of the function max_mtu is set to
custom value from HW. If rc != it will reach the if after goto label and
set max_mtu to default.

In my opinion this change is good. It is easier to see that the variable
is alwyas correct initialized, but I don't think it is a fix for real
issue.

Thanks,
Michal

> 
> 1500 is the industry standard networking mtu and therefore should be the
> default. If the function detects that the hardware custom sets the mtu,
> then it will use it instead.
> 
> Addresses-Coverity-ID: 1636407 ("Uninitialized scalar variable")
> Fixes: ab58a416c93f ("octeontx2-pf: cn10k: Get max mtu supported from admin function")
> Signed-off-by: Ethan Carter Edwards <ethan@...ancedwards.com>
> ---
>  drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> index 2b49bfec78692cf1f63c793ec49511607cda7c3e..6c1b03690a9c24c5232ff9f07befb1cc553490f7 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> @@ -1909,7 +1909,7 @@ u16 otx2_get_max_mtu(struct otx2_nic *pfvf)
>  {
>  	struct nix_hw_info *rsp;
>  	struct msg_req *req;
> -	u16 max_mtu;
> +	u16 max_mtu = 1500;
>  	int rc;
>  
>  	mutex_lock(&pfvf->mbox.lock);
> @@ -1948,7 +1948,6 @@ u16 otx2_get_max_mtu(struct otx2_nic *pfvf)
>  	if (rc) {
>  		dev_warn(pfvf->dev,
>  			 "Failed to get MTU from hardware setting default value(1500)\n");
> -		max_mtu = 1500;
>  	}
>  	return max_mtu;
>  }
> 
> ---
> base-commit: febbc555cf0fff895546ddb8ba2c9a523692fb55
> change-id: 20250210-otx2_common-453132aa0a24
> 
> Best regards,
> -- 
> Ethan Carter Edwards <ethan@...ancedwards.com>