Re: [PATCH v4 1/2] kasan: detect negative size in memory operation function

[Walter Wu]

On Fri, 2019-11-22 at 01:20 +0300, Andrey Ryabinin wrote:
> 
> On 11/12/19 9:53 AM, Walter Wu wrote:
> > KASAN missed detecting size is a negative number in memset(), memcpy(),
> > and memmove(), it will cause out-of-bounds bug. So needs to be detected
> > by KASAN.
> > 
> > If size is a negative number, then it has a 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.
> > 
> > KASAN report is shown below:
> > 
> >  BUG: KASAN: 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>
> > Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> > Cc: Alexander Potapenko <glider@xxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> 
> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>

Hi Andrey, Dmitry,

Thanks for your review and suggestion.

Walter