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SubjectRe: [PATCH] scsi: remove memset before memcpy
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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