[Devel] [PATCH RHEL7 COMMIT] ms/debugobjects: Make kmemleak ignore debug objects

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.1.1.vz7.37.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.1.1.vz7.37.28
------>
commit 2c1cd8780a9a0a5a86da8a04b7d10119ce9b8362
Author: Waiman Long <longman at redhat.com>
Date:   Wed Nov 15 16:14:55 2017 +0300

    ms/debugobjects: Make kmemleak ignore debug objects
    
    The allocated debug objects are either on the free list or in the
    hashed bucket lists. So they won't get lost. However if both debug
    objects and kmemleak are enabled and kmemleak scanning is done
    while some of the debug objects are transitioning from one list to
    the others, false negative reporting of memory leaks may happen for
    those objects. For example,
    
    [38687.275678] kmemleak: 12 new suspected memory leaks (see
    /sys/kernel/debug/kmemleak)
    unreferenced object 0xffff92e98aabeb68 (size 40):
      comm "ksmtuned", pid 4344, jiffies 4298403600 (age 906.430s)
      hex dump (first 32 bytes):
        00 00 00 00 00 00 00 00 d0 bc db 92 e9 92 ff ff  ................
        01 00 00 00 00 00 00 00 38 36 8a 61 e9 92 ff ff  ........86.a....
      backtrace:
        [<ffffffff8fa5378a>] kmemleak_alloc+0x4a/0xa0
        [<ffffffff8f47c019>] kmem_cache_alloc+0xe9/0x320
        [<ffffffff8f62ed96>] __debug_object_init+0x3e6/0x400
        [<ffffffff8f62ef01>] debug_object_activate+0x131/0x210
        [<ffffffff8f330d9f>] __call_rcu+0x3f/0x400
        [<ffffffff8f33117d>] call_rcu_sched+0x1d/0x20
        [<ffffffff8f4a183c>] put_object+0x2c/0x40
        [<ffffffff8f4a188c>] __delete_object+0x3c/0x50
        [<ffffffff8f4a18bd>] delete_object_full+0x1d/0x20
        [<ffffffff8fa535c2>] kmemleak_free+0x32/0x80
        [<ffffffff8f47af07>] kmem_cache_free+0x77/0x350
        [<ffffffff8f453912>] unlink_anon_vmas+0x82/0x1e0
        [<ffffffff8f440341>] free_pgtables+0xa1/0x110
        [<ffffffff8f44af91>] exit_mmap+0xc1/0x170
        [<ffffffff8f29db60>] mmput+0x80/0x150
        [<ffffffff8f2a7609>] do_exit+0x2a9/0xd20
    
    The references in the debug objects may also hide a real memory leak.
    
    As there is no point in having kmemleak to track debug object
    allocations, kmemleak checking is now disabled for debug objects.
    
    Signed-off-by: Waiman Long <longman at redhat.com>
    Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
    Cc: Andrew Morton <akpm at linux-foundation.org>
    Link: http://lkml.kernel.org/r/1502718733-8527-1-git-send-email-longman@redhat.com
    
    https://jira.sw.ru/browse/PSBM-76924
    (cherry picked from commit caba4cbbd27d755572730801ac34fe063fc40a32)
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 init/main.c        | 2 +-
 lib/debugobjects.c | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/init/main.c b/init/main.c
index dd890da..364d4a7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -615,8 +615,8 @@ asmlinkage void __init start_kernel(void)
 	}
 #endif
 	page_cgroup_init();
-	debug_objects_mem_init();
 	kmemleak_init();
+	debug_objects_mem_init();
 	setup_per_cpu_pageset();
 	numa_policy_init();
 	if (late_time_init)
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index a8c4b2f..a1b85ba 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -14,6 +14,7 @@
 #include <linux/debugfs.h>
 #include <linux/slab.h>
 #include <linux/hash.h>
+#include <linux/kmemleak.h>
 
 #define ODEBUG_HASH_BITS	14
 #define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)
@@ -106,6 +107,7 @@ static void fill_pool(void)
 		if (!new)
 			return;
 
+		kmemleak_ignore(new);
 		raw_spin_lock_irqsave(&pool_lock, flags);
 		hlist_add_head(&new->node, &obj_pool);
 		debug_objects_alloc++;
@@ -1047,6 +1049,7 @@ static int __init debug_objects_replace_static_objects(void)
 		obj = kmem_cache_zalloc(obj_cache, GFP_KERNEL);
 		if (!obj)
 			goto free;
+		kmemleak_ignore(obj);
 		hlist_add_head(&obj->node, &objects);
 	}