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Message-ID: <20170829195955.GA26858@himanshu-Vostro-3559>
Date: Wed, 30 Aug 2017 01:29:55 +0530
From: Himanshu Jha <himanshujha199640@...il.com>
To: Joe Perches <joe@...ches.com>
Cc: jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com,
kashyap.desai@...adcom.com, anil.gurumurthy@...gic.com,
sudarsana.kalluru@...gic.com, sumit.saxena@...adcom.com,
QLogic-Storage-Upstream@...gic.com, linux-scsi@...r.kernel.org,
linux-kernel@...r.kernel.org, megaraidlinux.pdl@...adcom.com
Subject: Re: [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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