On Mon, Oct 14, 2019 at 12:36 PM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > KASAN missed detecting size is negative numbers in memset(), memcpy(), > and memmove(), it will cause out-of-bounds bug, so needs to be detected > by KASAN. > > If 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. > > KASAN report: > > BUG: KASAN: heap-out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0 > Read of size 18446744073709551608 at addr ffffff8069660904 by task cat/72 > > CPU: 2 PID: 72 Comm: cat Not tainted 5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1 > Hardware name: linux,dummy-virt (DT) > Call trace: > dump_backtrace+0x0/0x288 > show_stack+0x14/0x20 > dump_stack+0x10c/0x164 > print_address_description.isra.9+0x68/0x378 > __kasan_report+0x164/0x1a0 > kasan_report+0xc/0x18 > check_memory_region+0x174/0x1d0 > memmove+0x34/0x88 > kmalloc_memmove_invalid_size+0x70/0xa0 > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=199341 > > Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> > Reported -by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > --- > mm/kasan/common.c | 13 ++++++++----- > mm/kasan/generic.c | 5 +++++ > mm/kasan/generic_report.c | 18 ++++++++++++++++++ > mm/kasan/tags.c | 5 +++++ > mm/kasan/tags_report.c | 18 ++++++++++++++++++ > 5 files changed, 54 insertions(+), 5 deletions(-) > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 6814d6d6a023..6ef0abd27f06 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -102,7 +102,8 @@ EXPORT_SYMBOL(__kasan_check_write); > #undef memset > void *memset(void *addr, int c, size_t len) > { > - check_memory_region((unsigned long)addr, len, true, _RET_IP_); > + if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_)) > + return NULL; > > return __memset(addr, c, len); > } > @@ -110,8 +111,9 @@ 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 (!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 +121,9 @@ 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 (!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)) { > + 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. > + */ > + if ((long)info->access_size < 0) > + 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/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)) { > + 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) > + return "heap-out-of-bounds"; > + > #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > struct kasan_alloc_meta *alloc_meta; > struct kmem_cache *cache; > -- > 2.18.0 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20191014103632.17930-1-walter-zh.wu%40mediatek.com.
