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Date: Wed, 2 Mar 2016 11:27:09 -0500
From: Jeff Cody <jcody@redhat.com>
Message-ID: <20160302162709.GH26318@localhost.localdomain>
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Subject: Re: [Qemu-devel] [PATCH v2 1/1] block/sheepdog: fix argument passed
 to qemu_strtoul()
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, qemu-block@nongnu.org, mitake.hitoshi@lab.ntt.co.jp, qemu-devel@nongnu.org, v.tolstov@selfip.ru, mreitz@redhat.com, namei.unix@gmail.com

On Wed, Mar 02, 2016 at 05:12:57PM +0100, Paolo Bonzini wrote:
> 
> 
> On 02/03/2016 17:09, Jeff Cody wrote:
> > +    ret = qemu_strtoul(snapshot_id, NULL, 10, &snap_id);
> > +    if (ret) {
> > +        error_setg_errno(errp, -ret, "Invalid snapshot ID: %s",
> > +                         snapshot_id ? snapshot_id : "<null>");
> > +        return ret;
> > +    }
> > +
> > +    if (snap_id > UINT32_MAX) {
> > +        error_setg_errno(errp, EINVAL, "Snapshot ID numeric value %" PRId64
> > +                         " exceeds Sheepdog maximum of %" PRId32, snap_id,
> > +                          UINT32_MAX);
> > +        return -EINVAL;
> >      }
> 
> I think including the errno produces a worse error message ("Invalid
> snapshot ID: foo: Invalid argument" or something like that), and also

Hey, if the user enters invalid input, they deserve a cryptic error
message! Oh, alright - sent a v3 :-)

> the error should be the same for an id of 10^10 (within uint64_t bounds)
> or 10^30 (outside the bounds).  So you could just use
> 
>     if (ret < 0 || snap_id > UINT32_MAX) {
>         error_setg(errp, "Invalid snapshot ID: %s",
>                    snapshot_id ? snapshot_id : "<null>");
>         return -EINVAL;
>     }
> 
> Thanks,
> 
> Paolo