Re: [PATCH] slub: fix SLAB_CONSISTENCY_CHECKS + KASAN_SW_TAGS
From: Andrey Konovalov
Date: Mon Feb 11 2019 - 10:47:23 EST
On Sat, Feb 9, 2019 at 5:41 AM Qian Cai <cai@xxxxxx> wrote:
>
> Enabling SLUB_DEBUG's SLAB_CONSISTENCY_CHECKS with KASAN_SW_TAGS
> triggers endless false positives during boot below due to
> check_valid_pointer() checks tagged pointers which have no addresses
> that is valid within slab pages.
>
> [ 0.000000] BUG radix_tree_node (Tainted: G B ): Freelist Pointer check fails
> [ 0.000000] -----------------------------------------------------------------------------
> [ 0.000000]
> [ 0.000000] INFO: Slab 0x(____ptrval____) objects=69 used=69 fp=0x (null) flags=0x7ffffffc000200
> [ 0.000000] INFO: Object 0x(____ptrval____) @offset=15060037153926966016 fp=0x(____ptrval____)
> [ 0.000000]
> [ 0.000000] Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 18 6b 06 00 08 80 ff d0 .........k......
> [ 0.000000] Object (____ptrval____): 18 6b 06 00 08 80 ff d0 00 00 00 00 00 00 00 00 .k..............
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Object (____ptrval____): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> [ 0.000000] Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........
> [ 0.000000] Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G B 5.0.0-rc5+ #18
> [ 0.000000] Call trace:
> [ 0.000000] dump_backtrace+0x0/0x450
> [ 0.000000] show_stack+0x20/0x2c
> [ 0.000000] __dump_stack+0x20/0x28
> [ 0.000000] dump_stack+0xa0/0xfc
> [ 0.000000] print_trailer+0x1bc/0x1d0
> [ 0.000000] object_err+0x40/0x50
> [ 0.000000] alloc_debug_processing+0xf0/0x19c
> [ 0.000000] ___slab_alloc+0x554/0x704
> [ 0.000000] kmem_cache_alloc+0x2f8/0x440
> [ 0.000000] radix_tree_node_alloc+0x90/0x2fc
> [ 0.000000] idr_get_free+0x1e8/0x6d0
> [ 0.000000] idr_alloc_u32+0x11c/0x2a4
> [ 0.000000] idr_alloc+0x74/0xe0
> [ 0.000000] worker_pool_assign_id+0x5c/0xbc
> [ 0.000000] workqueue_init_early+0x49c/0xd50
> [ 0.000000] start_kernel+0x52c/0xac4
> [ 0.000000] FIX radix_tree_node: Marking all objects used
> [ 0.000000]
>
> Signed-off-by: Qian Cai <cai@xxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Thanks!
> ---
> mm/slub.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 1e3d0ec4e200..075ebc529788 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -507,6 +507,7 @@ static inline int check_valid_pointer(struct kmem_cache *s,
> return 1;
>
> base = page_address(page);
> + object = kasan_reset_tag(object);
> object = restore_red_left(s, object);
> if (object < base || object >= base + page->objects * s->size ||
> (object - base) % s->size) {
> --
> 2.17.2 (Apple Git-113)
>