From 459372545c9c0d6f491e280dccc8a54a61b60e56 Mon Sep 17 00:00:00 2001
From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Date: Fri, 20 Nov 2015 15:57:18 -0800
Subject: [PATCH] kasan: fix kmemleak false-positive in kasan_module_alloc()

Kmemleak reports the following leak:

	unreferenced object 0xfffffbfff41ea000 (size 20480):
	comm "modprobe", pid 65199, jiffies 4298875551 (age 542.568s)
	hex dump (first 32 bytes):
	  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
	  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
	backtrace:
	  [<ffffffff82354f5e>] kmemleak_alloc+0x4e/0xc0
	  [<ffffffff8152e718>] __vmalloc_node_range+0x4b8/0x740
	  [<ffffffff81574072>] kasan_module_alloc+0x72/0xc0
	  [<ffffffff810efe68>] module_alloc+0x78/0xb0
	  [<ffffffff812f6a24>] module_alloc_update_bounds+0x14/0x70
	  [<ffffffff812f8184>] layout_and_allocate+0x16f4/0x3c90
	  [<ffffffff812faa1f>] load_module+0x2ff/0x6690
	  [<ffffffff813010b6>] SyS_finit_module+0x136/0x170
	  [<ffffffff8239bbc9>] system_call_fastpath+0x16/0x1b
	  [<ffffffffffffffff>] 0xffffffffffffffff

kasan_module_alloc() allocates shadow memory for module and frees it on
module unloading.  It doesn't store the pointer to allocated shadow memory
because it could be calculated from the shadowed address, i.e.
kasan_mem_to_shadow(addr).

Since kmemleak cannot find pointer to allocated shadow, it thinks that
memory leaked.

Use kmemleak_ignore() to tell kmemleak that this is not a leak and shadow
memory doesn't contain any pointers.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/kasan/kasan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index d41b21bce6a0..bc0a8d8b8f42 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -19,6 +19,7 @@
 #include <linux/export.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/kmemleak.h>
 #include <linux/memblock.h>
 #include <linux/memory.h>
 #include <linux/mm.h>
@@ -444,6 +445,7 @@ int kasan_module_alloc(void *addr, size_t size)
 
 	if (ret) {
 		find_vm_area(addr)->flags |= VM_KASAN;
+		kmemleak_ignore(ret);
 		return 0;
 	}
 
-- 
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