From 9e15afa5a87a3bf969a3b33c3dadfb8b46df42c0 Mon Sep 17 00:00:00 2001 From: Qian Cai Date: Thu, 6 Aug 2020 23:25:54 -0700 Subject: mm/page_alloc: silence a KASAN false positive kernel_init_free_pages() will use memset() on s390 to clear all pages from kmalloc_order() which will override KASAN redzones because a redzone was setup from the end of the allocation size to the end of the last page. Silence it by not reporting it there. An example of the report is, BUG: KASAN: slab-out-of-bounds in __free_pages_ok Write of size 4096 at addr 000000014beaa000 Call Trace: show_stack+0x152/0x210 dump_stack+0x1f8/0x248 print_address_description.isra.13+0x5e/0x4d0 kasan_report+0x130/0x178 check_memory_region+0x190/0x218 memset+0x34/0x60 __free_pages_ok+0x894/0x12f0 kfree+0x4f2/0x5e0 unpack_to_rootfs+0x60e/0x650 populate_rootfs+0x56/0x358 do_one_initcall+0x1f4/0xa20 kernel_init_freeable+0x758/0x7e8 kernel_init+0x1c/0x170 ret_from_fork+0x24/0x28 Memory state around the buggy address: 000000014bea9f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 000000014bea9f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >000000014beaa000: 03 fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe ^ 000000014beaa080: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe 000000014beaa100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Tested-by: Vasily Gorbik Acked-by: Vasily Gorbik Cc: Dmitry Vyukov Cc: Christian Borntraeger Cc: Alexander Potapenko Cc: Kees Cook Cc: Heiko Carstens Link: http://lkml.kernel.org/r/20200610052154.5180-1-cai@lca.pw Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 53c89de89e46..9a39009b1562 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1156,8 +1156,11 @@ static void kernel_init_free_pages(struct page *page, int numpages) { int i; + /* s390's use of memset() could override KASAN redzones. */ + kasan_disable_current(); for (i = 0; i < numpages; i++) clear_highpage(page + i); + kasan_enable_current(); } static __always_inline bool free_pages_prepare(struct page *page, -- cgit v1.2.3