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Sat, 09 Nov 2019 01:32:35 +0300 Subject: Re: [PATCH v3 1/2] kasan: detect negative size in memory operation function To: Walter Wu , Alexander Potapenko , Dmitry Vyukov , Matthias Brugger Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wsd_upstream References: <20191104020519.27988-1-walter-zh.wu@mediatek.com> From: Andrey Ryabinin Message-ID: <34bf9c08-d2f2-a6c6-1dbe-29b1456d8284@virtuozzo.com> Date: Sat, 9 Nov 2019 01:31:12 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191104020519.27988-1-walter-zh.wu@mediatek.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/4/19 5:05 AM, Walter Wu wrote: > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 6814d6d6a023..4ff67e2fd2db 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -99,10 +99,14 @@ bool __kasan_check_write(const volatile void *p, unsigned int size) > } > EXPORT_SYMBOL(__kasan_check_write); > > +extern bool report_enabled(void); > + > #undef memset > void *memset(void *addr, int c, size_t len) > { > - check_memory_region((unsigned long)addr, len, true, _RET_IP_); > + if (report_enabled() && > + !check_memory_region((unsigned long)addr, len, true, _RET_IP_)) > + return NULL; > > return __memset(addr, c, len); > } > @@ -110,8 +114,10 @@ void *memset(void *addr, int c, size_t len) > #undef memmove > void *memmove(void *dest, const void *src, size_t len) > { > - check_memory_region((unsigned long)src, len, false, _RET_IP_); > - check_memory_region((unsigned long)dest, len, true, _RET_IP_); > + if (report_enabled() && > + (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || > + !check_memory_region((unsigned long)dest, len, true, _RET_IP_))) > + return NULL; > > return __memmove(dest, src, len); > } > @@ -119,8 +125,10 @@ void *memmove(void *dest, const void *src, size_t len) > #undef memcpy > void *memcpy(void *dest, const void *src, size_t len) > { > - check_memory_region((unsigned long)src, len, false, _RET_IP_); > - check_memory_region((unsigned long)dest, len, true, _RET_IP_); > + if (report_enabled() && report_enabled() checks seems to be useless. > + (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || > + !check_memory_region((unsigned long)dest, len, true, _RET_IP_))) > + return NULL; > > return __memcpy(dest, src, len); > } > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index 616f9dd82d12..02148a317d27 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -173,6 +173,11 @@ static __always_inline bool check_memory_region_inline(unsigned long addr, > if (unlikely(size == 0)) > return true; > > + if (unlikely((long)size < 0)) { if (unlikely(addr + size < addr)) { > + kasan_report(addr, size, write, ret_ip); > + return false; > + } > + > if (unlikely((void *)addr < > kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { > kasan_report(addr, size, write, ret_ip); > diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c > index 36c645939bc9..52a92c7db697 100644 > --- a/mm/kasan/generic_report.c > +++ b/mm/kasan/generic_report.c > @@ -107,6 +107,24 @@ static const char *get_wild_bug_type(struct kasan_access_info *info) > > const char *get_bug_type(struct kasan_access_info *info) > { > + /* > + * If access_size is negative numbers, then it has three reasons > + * to be defined as heap-out-of-bounds bug type. > + * 1) 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. > + * 2) If KASAN has new bug type and user-space passes negative size, > + * then there are duplicate reports. So don't produce new bug type > + * in order to prevent duplicate reports by some systems > + * (e.g. syzbot) to report the same bug twice. > + * 3) When size is negative numbers, it may be passed from user-space. > + * So we always print heap-out-of-bounds in order to prevent that > + * kernel-space and user-space have the same bug but have duplicate > + * reports. > + */ Completely fail to understand 2) and 3). 2) talks something about *NOT* producing new bug type, but at the same time you code actually does that. 3) says something about user-space which have nothing to do with kasan. > + if ((long)info->access_size < 0) if (info->access_addr + info->access_size < info->access_addr) > + return "heap-out-of-bounds"; > + > if (addr_has_shadow(info->access_addr)) > return get_shadow_bug_type(info); > return get_wild_bug_type(info); > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 621782100eaa..c79e28814e8f 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -446,7 +446,7 @@ static void print_shadow_for_address(const void *addr) > } > } > > -static bool report_enabled(void) > +bool report_enabled(void) > { > if (current->kasan_depth) > return false; > diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c > index 0e987c9ca052..b829535a3ad7 100644 > --- a/mm/kasan/tags.c > +++ b/mm/kasan/tags.c > @@ -86,6 +86,11 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, > if (unlikely(size == 0)) > return true; > > + if (unlikely((long)size < 0)) { if (unlikely(addr + size < addr)) { > + kasan_report(addr, size, write, ret_ip); > + return false; > + } > + > tag = get_tag((const void *)addr); > > /* > diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c > index 969ae08f59d7..f7ae474aef3a 100644 > --- a/mm/kasan/tags_report.c > +++ b/mm/kasan/tags_report.c > @@ -36,6 +36,24 @@ > > const char *get_bug_type(struct kasan_access_info *info) > { > + /* > + * If access_size is negative numbers, then it has three reasons > + * to be defined as heap-out-of-bounds bug type. > + * 1) 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. > + * 2) If KASAN has new bug type and user-space passes negative size, > + * then there are duplicate reports. So don't produce new bug type > + * in order to prevent duplicate reports by some systems > + * (e.g. syzbot) to report the same bug twice. > + * 3) When size is negative numbers, it may be passed from user-space. > + * So we always print heap-out-of-bounds in order to prevent that > + * kernel-space and user-space have the same bug but have duplicate > + * reports. > + */ > + if ((long)info->access_size < 0) if (info->access_addr + info->access_size < info->access_addr) > + return "heap-out-of-bounds"; > + > #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > struct kasan_alloc_meta *alloc_meta; > struct kmem_cache *cache; >