linux-kernel - Re: [Linux-kernel-mentees][PATCH v2] packet: Fix undefined behavior in bit shift

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Date:   Wed, 26 Jun 2019 21:32:52 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Jiunn Chang <c0d1n61at3@...il.com>
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        davem@...emloft.net,
        "skh >> Shuah Khan" <skhan@...uxfoundation.org>
Subject: Re: [Linux-kernel-mentees][PATCH v2] packet: Fix undefined behavior
 in bit shift

On 6/26/19 9:25 PM, Jiunn Chang wrote:
> Shifting signed 32-bit value by 31 bits is undefined.  Changing most
> significant bit to unsigned.
> 
> Changes included in v2:
>    - use subsystem specific subject lines
>    - CC required mailing lists
> 

These version change lines don't belong in the change log.

> Signed-off-by: Jiunn Chang <c0d1n61at3@...il.com>
> ---

Move them here.

>   include/uapi/linux/if_packet.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
> index 467b654bd4c7..3d884d68eb30 100644
> --- a/include/uapi/linux/if_packet.h
> +++ b/include/uapi/linux/if_packet.h
> @@ -123,7 +123,7 @@ struct tpacket_auxdata {
>   /* Rx and Tx ring - header status */
>   #define TP_STATUS_TS_SOFTWARE		(1 << 29)
>   #define TP_STATUS_TS_SYS_HARDWARE	(1 << 30) /* deprecated, never set */
> -#define TP_STATUS_TS_RAW_HARDWARE	(1 << 31)
> +#define TP_STATUS_TS_RAW_HARDWARE	(1U << 31)
>   
>   /* Rx ring - feature request bits */
>   #define TP_FT_REQ_FILL_RXHASH	0x1
> 

thanks,
-- Shuah