4.9-stable review patch. If anyone has any objections, please let me know.
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From: Zhen Lei thunder.leizhen@huawei.com
[ Upstream commit 1e8e18f694a52d703665012ca486826f64bac29d ]
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 to a kernel crash 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: __asan_storeN+0x174/0x1a8 memset+0x24/0x48 layout_and_allocate+0xcd8/0x1800 load_module+0x190/0x23e8 SyS_finit_module+0x148/0x180
Link: http://lkml.kernel.org/r/1529659626-12660-1-git-send-email-thunder.leizhen@h... Signed-off-by: Zhen Lei thunder.leizhen@huawei.com Reviewed-by: Dmitriy Vyukov dvyukov@google.com Acked-by: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Alexander Potapenko glider@google.com Cc: Hanjun Guo guohanjun@huawei.com Cc: Libin huawei.libin@huawei.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/kasan/kasan.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -660,12 +660,13 @@ 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;