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Date:   Fri,  8 Feb 2019 23:41:28 -0500
From:   Qian Cai <cai@....pw>
To:     akpm@...ux-foundation.org, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com
Cc:     andreyknvl@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Qian Cai <cai@....pw>
Subject: [PATCH] slub: fix SLAB_CONSISTENCY_CHECKS + KASAN_SW_TAGS

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>
---
 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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