linux-kernel - Re: [PATCH 7/10] cciss: use safer test on the result of find_first_zero

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Message-ID: <alpine.DEB.2.10.1406041709500.2441@hadrien>
Date:	Wed, 4 Jun 2014 17:10:17 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	scameron@...rdog.cce.hp.com
cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk
Subject: Re: [PATCH 7/10] cciss: use safer test on the result of
 find_first_zero_bit



On Wed, 4 Jun 2014, scameron@...rdog.cce.hp.com wrote:

> > Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
> > return a larger number than the maximum position argument if that position
> > is not a multiple of BITS_PER_LONG.
> >
> > The semantic match that finds this problem is as follows:
> > (http://coccinelle.lip6.fr/)
> >
> > // <smpl>
> > @@
> > expression e1,e2,e3;
> > statement S1,S2;
> > @@
> >
> > e1 = find_first_zero_bit(e2,e3)
> > ...
> > if (e1
> > - ==
> > + >=
> >   e3)
> > S1 else S2
> > // </smpl>
> >
> > Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
> >
> > ---
> >  drivers/block/cciss.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff -u -p a/drivers/block/cciss.c b/drivers/block/cciss.c
> > --- a/drivers/block/cciss.c
> > +++ b/drivers/block/cciss.c
> > @@ -980,7 +980,7 @@ static CommandList_struct *cmd_alloc(ctl
> >
> >  	do {
> >  		i = find_first_zero_bit(h->cmd_pool_bits, h->nr_cmds);
> > -		if (i == h->nr_cmds)
> > +		if (i >= h->nr_cmds)
> >  			return NULL;
> >  	} while (test_and_set_bit(i, h->cmd_pool_bits) != 0);
> >  	c = h->cmd_pool + i;
>
>
> Thanks. Ack.
>
> You can add
>
> Reviewed-by: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
>
> to this patch if you want.
>
> You might consider adding "Cc: stable@...r.kernel.org" into the
> sign-off area as well.

Likewise here, the change is not needed.

julia
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