linux-kernel - Re: [PATCH] [SCSI] libsas: fix test for negative unsigned and typos

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Date:	Wed, 03 Dec 2008 10:19:01 -0600
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	roel kluin <roel.kluin@...il.com>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [SCSI] libsas: fix test for negative unsigned and typos

On Sat, 2008-11-29 at 11:31 -0500, roel kluin wrote:
> unsigned req->data_len cannot be negative, and fix typo
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> I am not sure whether this is what was intended, please review.

I think it was.  The fix looks like we need it.  However:

> diff --git a/drivers/scsi/libsas/sas_host_smp.c b/drivers/scsi/libsas/sas_host_smp.c
> index 16f9312..6eb0779 100644
> --- a/drivers/scsi/libsas/sas_host_smp.c
> +++ b/drivers/scsi/libsas/sas_host_smp.c
> @@ -199,12 +199,12 @@ int sas_smp_host_handler(struct Scsi_Host *shost, struct request *req,
>  		break;
>  
>  	case SMP_DISCOVER:
> -		req->data_len =- 16;
> -		if (req->data_len < 0) {
> +		if (req->data_len < 15) {
>  			req->data_len = 0;
>  			error = -EINVAL;
>  			goto out;
>  		}

What I don't like about this code is the magic numbers for lengths.
This patch now doubles them (and makes them even more magic by having <
n-1).  How about fixing it like this instead:

if ((int)req->data_len < 0) {
...

That way the signed comparison just works if there was a negative
overflow?

Thanks,

James


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