linux-kernel - Re: [PATCH next] ca8210: Fix unsigned mac_len comparison with zero in ca8210_skb

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Message-ID: <ZAb5BlS+OgFfJM6t@corigine.com>
Date:   Tue, 7 Mar 2023 09:42:46 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc:     Dan Carpenter <error27@...il.com>,
        Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Harry Morris <harrymorris12@...il.com>,
        linux-wpan@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] ca8210: Fix unsigned mac_len comparison with zero
 in ca8210_skb_tx()

On Mon, Mar 06, 2023 at 11:18:24AM -0800, Harshit Mogalapalli wrote:
> mac_len is of type unsigned, which can never be less than zero.
> 
> 	mac_len = ieee802154_hdr_peek_addrs(skb, &header);
> 	if (mac_len < 0)
> 		return mac_len;
> 
> Change this to type int as ieee802154_hdr_peek_addrs() can return negative
> integers, this is found by static analysis with smatch.
> 
> Fixes: ded845a781a5 ("ieee802154: Add CA8210 IEEE 802.15.4 device driver")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>

I discussed this briefly with Harshit offline.

The commit referenced above tag does add the call to
ieee802154_hdr_peek_addrs(), an there is a sign miss match between
the return value and the variable.

The code to check the mac_len was added more recently, by the following
commit. However the fixes tag is probably fine as-is, because it's fixing
error handling of a call made in that commit.

6c993779ea1d ("ca8210: fix mac_len negative array access")

Reviewed-by: Simon Horman <simon.horman@...igine.com>