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@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1502718733-8527-1-git-send-email-longman@redhat.com

diff --git a/init/main.c b/init/main.c
index 052481fbe3633f64b420c5bbd6deea3be261e6a9..7ec20cf7b111360a837fa25af3ec20a830e901e3 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -651,8 +651,8 @@ asmlinkage __visible void __init start_kernel(void)
        }
 #endif
        page_ext_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 17afb043016133f880c3c64b696b5093f28dc52e..2f5349c6e81ae01b0cca972570f3b7920aca246e 100644 (file)
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -18,6 +18,7 @@
 #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)
@@ -110,6 +111,7 @@ 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_allocated++;
@@ -1080,6 +1082,7 @@ 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);
        }