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Thu, 01 Oct 2020 10:41:07 -0700 (PDT) Date: Thu, 1 Oct 2020 19:41:02 +0200 From: elver@google.com To: Andrey Konovalov Subject: Re: [PATCH v3 12/39] kasan: hide invalid free check implementation Message-ID: <20201001174102.GJ4162920@elver.google.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.5 (2020-06-23) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201001_134109_751329_F9D18BBB X-CRM114-Status: GOOD ( 25.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org, Branislav Rankov , Elena Petrova , Catalin Marinas , Kevin Brodsky , Will Deacon , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Alexander Potapenko , Evgenii Stepanov , Andrey Ryabinin , Andrew Morton , Vincenzo Frascino , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote: > This is a preparatory commit for the upcoming addition of a new hardware > tag-based (MTE-based) KASAN mode. > > For software KASAN modes the check is based on the value in the shadow > memory. Hardware tag-based KASAN won't be using shadow, so hide the > implementation of the check in check_invalid_free(). > > Also simplify the code for software tag-based mode. > > No functional changes for software modes. > > Signed-off-by: Andrey Konovalov > Signed-off-by: Vincenzo Frascino Reviewed-by: Marco Elver > --- > Change-Id: I5fae9531c9fc948eb4d4e0c589744032fc5a0789 > --- > mm/kasan/common.c | 19 +------------------ > mm/kasan/generic.c | 7 +++++++ > mm/kasan/kasan.h | 2 ++ > mm/kasan/sw_tags.c | 9 +++++++++ > 4 files changed, 19 insertions(+), 18 deletions(-) > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 123abfb760d4..543e6bf2168f 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -272,25 +272,9 @@ void * __must_check kasan_init_slab_obj(struct kmem_cache *cache, > return (void *)object; > } > > -static inline bool shadow_invalid(u8 tag, s8 shadow_byte) > -{ > - if (IS_ENABLED(CONFIG_KASAN_GENERIC)) > - return shadow_byte < 0 || > - shadow_byte >= KASAN_GRANULE_SIZE; > - > - /* else CONFIG_KASAN_SW_TAGS: */ > - if ((u8)shadow_byte == KASAN_TAG_INVALID) > - return true; > - if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte)) > - return true; > - > - return false; > -} > - > static bool __kasan_slab_free(struct kmem_cache *cache, void *object, > unsigned long ip, bool quarantine) > { > - s8 shadow_byte; > u8 tag; > void *tagged_object; > unsigned long rounded_up_size; > @@ -309,8 +293,7 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object, > if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU)) > return false; > > - shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object)); > - if (shadow_invalid(tag, shadow_byte)) { > + if (check_invalid_free(tagged_object)) { > kasan_report_invalid_free(tagged_object, ip); > return true; > } > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index ec4417156943..e1af3b6c53b8 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -187,6 +187,13 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, > return check_memory_region_inline(addr, size, write, ret_ip); > } > > +bool check_invalid_free(void *addr) > +{ > + s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr)); > + > + return shadow_byte < 0 || shadow_byte >= KASAN_GRANULE_SIZE; > +} > + > void kasan_cache_shrink(struct kmem_cache *cache) > { > quarantine_remove_cache(cache); > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 1865bb92d47a..3eff57e71ff5 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -164,6 +164,8 @@ void kasan_poison_memory(const void *address, size_t size, u8 value); > bool check_memory_region(unsigned long addr, size_t size, bool write, > unsigned long ret_ip); > > +bool check_invalid_free(void *addr); > + > void *find_first_bad_addr(void *addr, size_t size); > const char *get_bug_type(struct kasan_access_info *info); > > diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c > index 4bdd7dbd6647..b2638c2cd58a 100644 > --- a/mm/kasan/sw_tags.c > +++ b/mm/kasan/sw_tags.c > @@ -121,6 +121,15 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, > return true; > } > > +bool check_invalid_free(void *addr) > +{ > + u8 tag = get_tag(addr); > + u8 shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(reset_tag(addr))); > + > + return (shadow_byte == KASAN_TAG_INVALID) || > + (tag != KASAN_TAG_KERNEL && tag != shadow_byte); > +} > + > #define DEFINE_HWASAN_LOAD_STORE(size) \ > void __hwasan_load##size##_noabort(unsigned long addr) \ > { \ > -- > 2.28.0.681.g6f77f65b4e-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel