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Message-ID: <CAAeHK+wKeqt2xvZfF5X4Z0dxLJqrdvDu894tFpGR172z0iVGRw@mail.gmail.com>
Date:   Mon, 11 Feb 2019 16:47:04 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slub: fix SLAB_CONSISTENCY_CHECKS + KASAN_SW_TAGS

On Sat, Feb 9, 2019 at 5:41 AM Qian Cai <cai@....pw> 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@....pw>

Reviewed-by: Andrey Konovalov <andreyknvl@...gle.com>

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)
>

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