linux-kernel - RE: [PATCH 2/2] staging: rtl8723bs: fix cast to restricted _

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Date:   Thu, 19 Aug 2021 09:43:37 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Aakash Hemadri' <aakashhemadri123@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Shuah Khan <skhan@...uxfoundation.org>,
        Bjorn Helgaas <bjorn@...gaas.com>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/2] staging: rtl8723bs: fix cast to restricted __le32

From: Aakash Hemadri
> Sent: 16 August 2021 18:35
> 
> Fix sparse warning:
> warning: cast to restricted __le32

How many different copies of this crappy copy are there?
> 
...
> diff --git a/drivers/staging/rtl8723bs/core/rtw_security.c
> b/drivers/staging/rtl8723bs/core/rtw_security.c
> index 381deeea99d0..5320b1a46dfb 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_security.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_security.c
> @@ -122,7 +122,7 @@ void rtw_wep_decrypt(struct adapter  *padapter, u8 *precvframe)
>  		arc4_crypt(ctx, payload, payload,  length);
> 
>  		/* calculate icv and compare the icv */
> -		*((u32 *)crc) = le32_to_cpu(~crc32_le(~0, payload, length - 4));
> +		*((u32 *)crc) = ~crc32_le(~0, payload, length - 4);

You've removed a byteswap which is needed on BE architectures.

>  	}
>  }
> @@ -621,7 +621,7 @@ u32 rtw_tkip_decrypt(struct adapter *padapter, u8 *precvframe)
>  			arc4_setkey(ctx, rc4key, 16);
>  			arc4_crypt(ctx, payload, payload, length);
> 
> -			*((u32 *)crc) = le32_to_cpu(~crc32_le(~0, payload, length - 4));
> +			*((u32 *)crc) = ~crc32_le(~0, payload, length - 4);
> 
>  			if (crc[3] != payload[length - 1] || crc[2] != payload[length - 2] ||
>  			    crc[1] != payload[length - 3] || crc[0] != payload[length - 4])

As above - crc32_le() does a 'little-endian crc' but returns a host-ordered value.
The (horrid) array cast means you need to store a LE value.

There are a dozen better ways to do this - I'm bored of quoting them.

	David

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