cipso: remove an unneeded NULL check in cipso_v4_doi_add()

We dereference doi_def on the line before the NULL check.  It has
been this way since 2008.  I checked all the callers and doi_def is
always non-NULL here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

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On Tue, Oct 11, 2011 at 9:22 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> We dereference doi_def on the line before the NULL check.  It has
> been this way since 2008.  I checked all the callers and doi_def is
> always non-NULL here.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
> index 2c2a98e..86f3b88 100644
> --- a/net/ipv4/cipso_ipv4.c
> +++ b/net/ipv4/cipso_ipv4.c
> @@ -476,7 +476,7 @@ int cipso_v4_doi_add(struct cipso_v4_doi *doi_def,
>        doi = doi_def->doi;
>        doi_type = doi_def->type;
>
> -       if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
> +       if (doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
>                goto doi_add_return;
>        for (iter = 0; iter < CIPSO_V4_TAG_MAXCNT; iter++) {
>                switch (doi_def->tags[iter]) {

I'd prefer to keep the NULL check in there as it does afford a little
bit of extra safety and this is management code after all, not
per-packet processing code, so the extra check should have no
observable performance impact.

On Tue, Oct 11, 2011 at 05:20:11PM -0400, Paul Moore wrote:
> > -       if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
> > +       if (doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
> >                goto doi_add_return;
> >        for (iter = 0; iter < CIPSO_V4_TAG_MAXCNT; iter++) {
> >                switch (doi_def->tags[iter]) {
> 
> I'd prefer to keep the NULL check in there as it does afford a little
> bit of extra safety and this is management code after all, not
> per-packet processing code, so the extra check should have no
> observable performance impact.

The dereferences on the lines before mean we would Oops before
reaching the check.  But I guess I can move the check forward.  The
error handling at goto doi_add_return relies on a non-NULL value for
doi_def but I could just put a return in front of the dereference.

	if (!doi_def)
		return -EINVAL;

I'll send a patch to do this tomorrow.

regards,
dan carpenter
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From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Wed, 12 Oct 2011 00:55:49 +0300

> On Tue, Oct 11, 2011 at 05:20:11PM -0400, Paul Moore wrote:
>> > -       if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
>> > +       if (doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
>> >                goto doi_add_return;
>> >        for (iter = 0; iter < CIPSO_V4_TAG_MAXCNT; iter++) {
>> >                switch (doi_def->tags[iter]) {
>> 
>> I'd prefer to keep the NULL check in there as it does afford a little
>> bit of extra safety and this is management code after all, not
>> per-packet processing code, so the extra check should have no
>> observable performance impact.
> 
> The dereferences on the lines before mean we would Oops before
> reaching the check.  But I guess I can move the check forward.  The
> error handling at goto doi_add_return relies on a non-NULL value for
> doi_def but I could just put a return in front of the dereference.
> 
> 	if (!doi_def)
> 		return -EINVAL;
> 
> I'll send a patch to do this tomorrow.

I think your original patch is still the best one.

Saying the NULL check should stay to provide "extra safety" is
complete garbage.  Especially since, as Dan shows, we dereference the
pointer before to damn check.

I'll therefore apply Dan's original patch.
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On Wednesday, October 12, 2011 12:55:49 AM Dan Carpenter wrote:
> On Tue, Oct 11, 2011 at 05:20:11PM -0400, Paul Moore wrote:
> > > -       if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
> > > +       if (doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
> > >                goto doi_add_return;
> > >        for (iter = 0; iter < CIPSO_V4_TAG_MAXCNT; iter++) {
> > >                switch (doi_def->tags[iter]) {
> > 
> > I'd prefer to keep the NULL check in there as it does afford a little
> > bit of extra safety and this is management code after all, not
> > per-packet processing code, so the extra check should have no
> > observable performance impact.
> 
> The dereferences on the lines before mean we would Oops before
> reaching the check ...

Thanks for pointing that out, I missed that when looking at your patch.