On 06/22/2018 12:27 PM, Zhen Lei wrote: > There is a special case that the size is "(N << KASAN_SHADOW_SCALE_SHIFT) > Pages plus X", the value of X is [1, KASAN_SHADOW_SCALE_SIZE-1]. The > operation "size >> KASAN_SHADOW_SCALE_SHIFT" will drop X, and the roundup > operation can not retrieve the missed one page. For example: size=0x28006, > PAGE_SIZE=0x1000, KASAN_SHADOW_SCALE_SHIFT=3, we will get > shadow_size=0x5000, but actually we need 6 pages. > > shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT, PAGE_SIZE); > > This can lead kernel to be crashed, when kasan is enabled and the value > of mod->core_layout.size or mod->init_layout.size is like above. Because > the shadow memory of X has not been allocated and mapped. > > move_module: > ptr = module_alloc(mod->core_layout.size); > ... > memset(ptr, 0, mod->core_layout.size); //crashed > > Unable to handle kernel paging request at virtual address ffff0fffff97b000 > ...... > Call trace: > [<ffff8000004694d4>] __asan_storeN+0x174/0x1a8 > [<ffff800000469844>] memset+0x24/0x48 > [<ffff80000025cf28>] layout_and_allocate+0xcd8/0x1800 > [<ffff80000025dbe0>] load_module+0x190/0x23e8 > [<ffff8000002601e8>] SyS_finit_module+0x148/0x180 > > Signed-off-by: Zhen Lei <[email protected]> > ---
Acked-by: Andrey Ryabinin <[email protected]> > mm/kasan/kasan.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 81a2f45..f5ac4ac 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -427,12 +427,13 @@ void kasan_kfree_large(const void *ptr) > int kasan_module_alloc(void *addr, size_t size) > { > void *ret; > + size_t scaled_size; > size_t shadow_size; > unsigned long shadow_start; > > shadow_start = (unsigned long)kasan_mem_to_shadow(addr); > - shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT, > - PAGE_SIZE); > + scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT; > + shadow_size = round_up(scaled_size, PAGE_SIZE); > > if (WARN_ON(!PAGE_ALIGNED(shadow_start))) > return -EINVAL; > -- > 1.8.3 > >
