Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <cover.1605305978.git.andreyknvl@google.com> <52518837b34d607abbf30855b3ac4cb1a9486946.1605305978.git.andreyknvl@google.com>
 <CACT4Y+ZaRgqpgPRe5k5fVrhd_He5_6N55715YzwWcQyvxYUNRQ@mail.gmail.com>
In-Reply-To: <CACT4Y+ZaRgqpgPRe5k5fVrhd_He5_6N55715YzwWcQyvxYUNRQ@mail.gmail.com>
From:   Marco Elver <elver@google.com>
Date:   Tue, 17 Nov 2020 14:18:32 +0100
Message-ID: <CANpmjNN6=5Vy5puLbhOQxSNUNptFA9jKKqnU4RXRcLb4JT=hJg@mail.gmail.com>
Subject: Re: [PATCH mm v3 17/19] kasan: clean up metadata allocation and usage
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Andrey Konovalov <andreyknvl@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, 17 Nov 2020 at 14:12, Dmitry Vyukov <dvyukov@google.com> wrote:

> > +        */
> >         *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;
> > +
> >         ___cache_free(cache, object, _THIS_IP_);
> >
> >         if (IS_ENABLED(CONFIG_SLAB))
> > @@ -168,6 +173,9 @@ void quarantine_put(struct kmem_cache *cache, void *object)
> >         struct qlist_head temp = QLIST_INIT;
> >         struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
> >
> > +       if (!meta)
> > +               return;
>
> Humm... is this possible? If yes, we would be leaking the object here...
> Perhaps BUG_ON with a comment instead.

If this is possible in prod-mode KASAN, a WARN_ON() that returns would be safer.