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Re: [PATCH] scsi: remove memset before memcpy

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On Tue, Aug 29, 2017 at 12:29:35PM -0700, Joe Perches wrote:
> On Wed, 2017-08-30 at 00:19 +0530, Himanshu Jha wrote:
> > drivers/scsi/megaraid/megaraid_sas_fusion.c
> 
> I don't know if you did this with coccinelle.

Yes, I did this with coccinelle.

> 
> If so, it would be good to show the tool and script
> in the commit message.

Alright, next time.
> 
> If not, the input script is pretty simple.
> 
> $ cat memset_before_memcpy.cocci
> @@
> expression e1;
> expression e2;
> expression e3;
> @@
> 
> -	memset(e1, 0, e3);
> 	memcpy(e1, e2, e3);
> $
> 
> Adding a test to make sure e1 or e3 isn't
> modified before any other code uses them
> by doing
> 
> $ cat memset_before_memcpy_2.cocci
> @@
> expression e1;
> expression e2;
> expressi
> on e3;
> @@
> 
> -	memset(e1, 0, e3);
> 	... when != \( e1 \| e3 \)
> 	memcpy(e1, e2, e3);
> $
> 
> finds more cases but there may be a
> false positive if e1 is a passed
> function argument and if the operation
> isn't effectively atomic like below:
>

I usually check all my diff before sending to see if any false positives
occured or not.

It's been 4 days since I learnt coccinelle and before I used to look
into every files for occurences or search the identifiers on
FreeElectrons.

From now I will mention whatever tool I used on my patch!

Thanks

> ----------------------------------------------------------------
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -2556,7 +2556,6 @@ void br_multicast_get_stats(const struct
>  	struct br_mcast_stats tdst;
>  	int i;
>  
> -	memset(dest, 0, sizeof(*dest));
>  	if (p)
>  		stats = p->mcast_stats;
>  	else
> 
> ----------------------------------------------------------------
> 
> where the memcpy is the last line of the function.
> 

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[PATCH] scsi: remove memset before memcpy Himanshu Jha <himanshujha199640@gmail.com> - 2017-08-29 20:50 +0200
  Re: [PATCH] scsi: remove memset before memcpy Joe Perches <joe@perches.com> - 2017-08-29 21:30 +0200
    Re: [PATCH] scsi: remove memset before memcpy Himanshu Jha <himanshujha199640@gmail.com> - 2017-08-29 22:10 +0200

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