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.
Showing the changes to lib/debugobjects.c (1 of 2 files). Show all
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| @@ -18,6 +18,7 @@ · 17 unmodified lines | ||
| 18 | 18 | #include <linux/debugfs.h> |
| 19 | 19 | #include <linux/slab.h> |
| 20 | 20 | #include <linux/hash.h> |
| 21 | +#include <linux/kmemleak.h> | |
| 21 | 22 | |
| 22 | 23 | #define ODEBUG_HASH_BITS 14 |
| 23 | 24 | #define ODEBUG_HASH_SIZE (1 << ODEBUG_HASH_BITS) |
| @@ -110,6 +111,7 @@ static void fill_pool(void) · 86 unmodified lines | ||
| 110 | 111 | if (!new) |
| 111 | 112 | return; |
| 112 | 113 | |
| 114 | + kmemleak_ignore(new); | |
| 113 | 115 | raw_spin_lock_irqsave(&pool_lock, flags); |
| 114 | 116 | hlist_add_head(&new->node, &obj_pool); |
| 115 | 117 | debug_objects_allocated++; |
| @@ -1080,6 +1082,7 @@ static int __init debug_objects_replace_static_objects(void) · 964 unmodified lines | ||
| 1080 | 1082 | obj = kmem_cache_zalloc(obj_cache, GFP_KERNEL); |
| 1081 | 1083 | if (!obj) |
| 1082 | 1084 | goto free; |
| 1085 | + kmemleak_ignore(obj); | |
| 1083 | 1086 | hlist_add_head(&obj->node, &objects); |
| 1084 | 1087 | } |
| 1085 | 1088 | |