netdev - RE: [PATCH net] enetc: Avoid implicit sign extension

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Date:   Mon, 29 Mar 2021 13:53:09 +0000
From:   Claudiu Manoil <claudiu.manoil@....com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: RE: [PATCH net] enetc: Avoid implicit sign extension

>-----Original Message-----
>From: Claudiu Manoil <claudiu.manoil@....com>
>Sent: Monday, March 29, 2021 4:35 PM
>To: netdev@...r.kernel.org
>Cc: Jakub Kicinski <kuba@...nel.org>; David S . Miller
><davem@...emloft.net>; Vladimir Oltean <vladimir.oltean@....com>
>Subject: [PATCH net] enetc: Avoid implicit sign extension
>
>Static analysis tool reports:
>"Suspicious implicit sign extension - 'flags' with type u8 (8 bit,
>unsigned) is promoted in 'flags' << 24 to type int (32 bits, signed),
>then sign-extended to type unsigned long long (64 bits, unsigned).
>If flags << 24 is greater than 0x7FFFFFFF, the upper bits of the result
>will all be 1."
>
>Use lower_32_bits() to avoid this scenario.
>

Fixes: 82728b91f124 ("enetc: Remove Tx checksumming offload code")