linux-kernel - Re: [PATCH] staging: r8188eu: Fix different base types in assignments and parameters

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Date:   Mon, 02 Aug 2021 16:26:33 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Larry Finger <Larry.Finger@...inger.net>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: r8188eu: Fix different base types in assignments and parameters

On Monday, August 2, 2021 4:05:05 PM CEST Dan Carpenter wrote:
> On Fri, Jul 30, 2021 at 08:14:52PM +0200, Fabio M. De Francesco wrote:
> > Fix sparse warnings of different base types in assignments
> > and in passing function parameters.
> 
> This patch fixes some endian bugs but it's not mentioned at all in the
> commit message.  Did you send to the correct patch?
> 

Too late to change the commit message: Greg K-H has already taken this patch 
as-is (please see commit  56febcc2595e).

> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> > ---
> > 
> >  drivers/staging/r8188eu/core/rtw_br_ext.c | 46 ++++++++++++++++++-----
> >  1 file changed, 36 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c
> > b/drivers/staging/r8188eu/core/rtw_br_ext.c index 
e00302137a60..31ca2e548555 100644
> >
> > [...]
> >
> >  static inline void __nat25_generate_ipx_network_addr_with_node(unsigned 
char
> >  *networkAddr,> 
> > -				unsigned int *ipxNetAddr, 
unsigned char *ipxNodeAddr)
> > +				__be32 *ipxNetAddr, unsigned char 
*ipxNodeAddr)
> > 
> >  {
> > 
> > +	union {
> > +                unsigned int f0;
> > +                unsigned char f1[IPX_NODE_LEN];
> 
> What is going on here??  Why is f1 six bytes?
> 

Please look at the third parameter of the latest memcpy() in this function.

> > +        } addr;
> > +
> > 
> >  	memset(networkAddr, 0, MAX_NETWORK_ADDR_LEN);
> >  	
> >  	networkAddr[0] = NAT25_IPX;
> > 
> > -	memcpy(networkAddr+1, (unsigned char *)ipxNetAddr, 4);
> > +	addr.f0 = be32_to_cpu(*ipxNetAddr);
> > +	memcpy(networkAddr+1, addr.f1, 4);
> 
> What's the point of a union?  memcpy() doesn't care about endian
> anotations.
> 
> >  	memcpy(networkAddr+5, ipxNodeAddr, 6);
			                     ^^^^^

I'm talking about this memcpy().

> >  }
> >  
> >  static inline void __nat25_generate_ipx_network_addr_with_socket(unsigned 
char
> >  *networkAddr,> 
> > -				unsigned int *ipxNetAddr, 
unsigned short *ipxSocketAddr)
> > +				__be32 *ipxNetAddr, __be16 
*ipxSocketAddr)
> > 
> >  {
> > 
> > +	union {
> > +		unsigned int f0;
> > +		unsigned char f1[4];
> > +	} addr;
> > +
> > 
> >  	memset(networkAddr, 0, MAX_NETWORK_ADDR_LEN);
> >  	
> >  	networkAddr[0] = NAT25_IPX;
> > 
> > -	memcpy(networkAddr+1, (unsigned char *)ipxNetAddr, 4);
> > -	memcpy(networkAddr+5, (unsigned char *)ipxSocketAddr, 2);
> > +	addr.f0 = be32_to_cpu(*ipxNetAddr);
> > +	memcpy(networkAddr+1, addr.f1, 4);
> > +	addr.f0 ^= addr.f0;
> 
> What on earth????

I can't see any problem in xor(ing) a field with itself. Perhaps I read too 
much Assembly code :-) . However, am I missing something? 

> > +	addr.f0 = be16_to_cpu(*ipxSocketAddr);
> 
> I'm so puzzled.
> 
> > +	memcpy(networkAddr+5, addr.f1, 2);
> 
> This patch is really weird so I'm done reviewing it.

I'm sorry that you don't like this patch, but Greg already had the last word 
on it.

> regards,
> dan carpenter

Regards,

Fabio