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[122.116.74.98]) by smtp.gmail.com with ESMTPSA id t13sm3566599pfq.173.2021.06.18.23.39.49 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 18 Jun 2021 23:39:50 -0700 (PDT) Date: Sat, 19 Jun 2021 14:39:42 +0800 From: Kuan-Ying Lee To: Marco Elver Cc: Greg Kroah-Hartman , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Andrew Morton , kasan-dev , LKML , Linux Memory Management List Subject: Re: [PATCH v2 2/3] kasan: integrate the common part of two KASAN tag-based modes Message-ID: <20210619063942.GA67@DESKTOP-PJLD54P.localdomain> References: <20210612045156.44763-1-kylee0686026@gmail.com> <20210612045156.44763-3-kylee0686026@gmail.com> <20210612155108.GA68@DESKTOP-PJLD54P.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 14, 2021 at 10:48:27AM +0200, Marco Elver wrote: > On Sat, 12 Jun 2021 at 17:51, Kuan-Ying Lee wrote: > [...] > > > > diff --git a/mm/kasan/report_tags.h b/mm/kasan/report_tags.h > > > > new file mode 100644 > > > > index 000000000000..4f740d4d99ee > > > > --- /dev/null > > > > +++ b/mm/kasan/report_tags.h > > > > @@ -0,0 +1,56 @@ > > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > > +#ifndef __MM_KASAN_REPORT_TAGS_H > > > > +#define __MM_KASAN_REPORT_TAGS_H > > > > + > > > > +#include "kasan.h" > > > > +#include "../slab.h" > > > > + > > > > +#ifdef CONFIG_KASAN_TAGS_IDENTIFY > > > > +const char *kasan_get_bug_type(struct kasan_access_info *info) > > > > +{ > > > [...] > > > > + /* > > > > + * If access_size is a negative number, then it has reason to be > > > > + * defined as out-of-bounds bug type. > > > > + * > > > > + * Casting negative numbers to size_t would indeed turn up as > > > > + * a large size_t and its value will be larger than ULONG_MAX/2, > > > > + * so that this can qualify as out-of-bounds. > > > > + */ > > > > + if (info->access_addr + info->access_size < info->access_addr) > > > > + return "out-of-bounds"; > > > > > > This seems to change behaviour for SW_TAGS because it was there even > > > if !CONFIG_KASAN_TAGS_IDENTIFY. Does it still work as before? > > > > > > > You are right. It will change the behavior. > > However, I think that if !CONFIG_KASAN_TAG_IDENTIFY, it should be reported > > "invalid-access". > > There's no reason that if !CONFIG_KASAN_TAG_IDENTIFY it should be > reported as "invalid-acces" if we can do better without the additional > state that the config option introduces. > > It's trivial to give a slightly better report without additional > state, see the comment explaining why it's reasonable to infer > out-of-bounds here. > > > Or is it better to keep it in both conditions? > > We want to make this patch a non-functional change. > Got it. > [...] > > > > diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c > > > > new file mode 100644 > > > > index 000000000000..9c33c0ebe1d1 > > > > --- /dev/null > > > > +++ b/mm/kasan/tags.c > > > > @@ -0,0 +1,58 @@ > > > > +// SPDX-License-Identifier: GPL-2.0 > > > > +/* > > > > + * This file contains common tag-based KASAN code. > > > > + * > > > > + * Author: Kuan-Ying Lee > > > > > > We appreciate your work on this, but this is misleading. Because you > > > merely copied/moved the code, have a look what sw_tags.c says -- that > > > should either be preserved, or we add nothing here. > > > > > > I prefer to add nothing or the bare minimum (e.g. if the company > > > requires a Copyright line) for non-substantial additions because this > > > stuff becomes out-of-date fast and just isn't useful at all. 'git log' > > > is the source of truth. > > > > This was my first time to upload a new file. > > Thanks for the suggestions. :) > > I will remove this author tag and wait for Greg's process advice. > > > > > > > > Cc'ing Greg for process advice. For moved code, does it have to > > > preserve the original Copyright line if there was one? > > Greg responded, see his emails. Please preserve the original header > from the file the code was moved from (hw_tags.c/sw_tags.c). Ok. I will do it in v3. Thanks. > > Thanks, > -- Marco