Date: Wed, 24 Jan 2018 18:33:35 -0700 From: Warner Losh <imp@bsdimp.com> To: Kristof Provost <kp@freebsd.org> Cc: Ian Lepore <ian@freebsd.org>, Gleb Smirnoff <glebius@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r328313 - head/sys/netpfil/pf Message-ID: <CANCZdfowMis2qxc0vd713S-GJBFp%2B7JZESg03V9QQpXD2ZDdDw@mail.gmail.com> In-Reply-To: <8FA39DD7-FD83-49D5-B7FC-3637B42129BE@FreeBSD.org> References: <201801240429.w0O4THIl059440@repo.freebsd.org> <20180125001310.GJ8113@FreeBSD.org> <1516840498.42536.213.camel@freebsd.org> <8FA39DD7-FD83-49D5-B7FC-3637B42129BE@FreeBSD.org>
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On Jan 24, 2018 6:08 PM, "Kristof Provost" <kp@freebsd.org> wrote:
On 25 Jan 2018, at 11:34, Ian Lepore wrote:
> On Wed, 2018-01-24 at 16:13 -0800, Gleb Smirnoff wrote:
>
>> (r328313)
>> K> @@ -1613,6 +1613,7 @@ int
>> K> pf_unlink_state(struct pf_state *s, u_int flags)
>> K> {
>> K> struct pf_idhash *ih = &V_pf_idhash[PF_IDHASH(s)];
>> K> + int last;
>> K>
>> K> if ((flags & PF_ENTER_LOCKED) == 0)
>> K> PF_HASHROW_LOCK(ih);
>> K> @@ -1653,7 +1654,8 @@ pf_unlink_state(struct pf_state *s, u_int
>> flags)
>> K> PF_HASHROW_UNLOCK(ih);
>> K>
>> K> pf_detach_state(s);
>> K> - refcount_release(&s->refs);
>> K> + last = refcount_release(&s->refs);
>> K> + KASSERT(last == 0, ("Incorrect state reference count"));
>> K>
>> K> return (pf_release_state(s));
>> K> }
>>
>> IMHO, we shouldn't emit extra code to please Coverity. We can mark it
>> as a false positive in the interface. It may make sense to add a
>> comment
>> for a human to explain why return isn't checked here.
>>
>>
> Not to mention that when KASSERT compiles to nothing, what you're left
> with is a "defined but not used" warning for 'last'.
>
> I’d really like to keep the KASSERT(), because this is the sort of thing
that could go wrong, and the assertion would be helpful.
I suppose I could wrap last in #ifdef INVARIANTS, but that’s rather ugly
too.
Asserting that the refcount is at least 1 when entering pf_release_state()
would express the same, but that’s also problematic.
Of course, errors should trigger the KASSERT() in refcount_release(), so I
think I may have convinced myself that the KASSERT() can in fact be removed
and replaced with (void)refcount_release() and a comment explaining why
this refcount_release() can never return 1.
It would be good to have a Coverty cheer sheet so we know how to annotate
this stuff correctly in the source. I've started fumbling my way through
for the boot loader and devmatch changes...
Warner
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