Re: [PATCH] mm/slab: Fix a kmemleak in kmem_cache_destroy()

xiaolei wang
2024-02-28T08:15:38Z

On 2/28/24 15:34, Vlastimil Babka wrote:
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> On 2/28/24 04:04, Xiaolei Wang wrote:
>> For earlier kmem cache creation, slab_sysfs_init() has not been called.
>> Consequently, kmem_cache_destroy() cannot utilize kobj_type::release to
>> release the kmem_cache structure. Therefore, tweak kmem_cache_release()
>> to use slab_kmem_cache_release() for releasing kmem_cache when slab_state
>> isn't FULL. This will fixes the memory leaks like following:
> So do I understand correctly the leak happens when a cache is destroyed
> while slab_state < FULL? Do we ever destroy a cache that early?

Yes, like some test programs, test_meminit_init() or
arm_v7s_alloc_pgtable(),

destroy will cause leaks after use, and when slab_state < FULL,

there are many places to create cache, which itself also has the risk of
leaks

thanks

xiaolei

>
>> unreferenced object 0xffff0000c2d87080 (size 128):
>> comm "swapper/0", pid 1, jiffies 4294893428
>> hex dump (first 32 bytes):
>> 00 00 00 00 ad 4e ad de ff ff ff ff 6b 6b 6b 6b .....N......kkkk
>> ff ff ff ff ff ff ff ff b8 ab 48 89 00 80 ff ff.....H.....
>> backtrace (crc 8819d0f6):
>> [<ffff80008317a298>] kmemleak_alloc+0xb0/0xc4
>> [<ffff8000807e553c>] kmem_cache_alloc_node+0x288/0x3a8
>> [<ffff8000807e95f0>] __kmem_cache_create+0x1e4/0x64c
>> [<ffff8000807216bc>] kmem_cache_create_usercopy+0x1c4/0x2cc
>> [<ffff8000807217e0>] kmem_cache_create+0x1c/0x28
>> [<ffff8000819f6278>] arm_v7s_alloc_pgtable+0x1c0/0x6d4
>> [<ffff8000819f53a0>] alloc_io_pgtable_ops+0xe8/0x2d0
>> [<ffff800084b2d2c4>] arm_v7s_do_selftests+0xe0/0x73c
>> [<ffff800080016b68>] do_one_initcall+0x11c/0x7ac
>> [<ffff800084a71ddc>] kernel_init_freeable+0x53c/0xbb8
>> [<ffff8000831728d8>] kernel_init+0x24/0x144
>> [<ffff800080018e98>] ret_from_fork+0x10/0x20
>>
>> Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
>> ---
>> mm/slab_common.c | 8 ++++++--
>> mm/slub.c | 6 ++----
>> 2 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>> index 238293b1dbe1..b6b35bcdd196 100644
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -404,8 +404,12 @@ EXPORT_SYMBOL(kmem_cache_create);
>> */
>> static void kmem_cache_release(struct kmem_cache *s)
>> {
>> - sysfs_slab_unlink(s);
>> - sysfs_slab_release(s);
>> + if (slab_state >= FULL) {
>> + sysfs_slab_unlink(s);
>> + sysfs_slab_release(s);
>> + } else {
>> + slab_kmem_cache_release(s);
>> + }
>> }
>> #else
>> static void kmem_cache_release(struct kmem_cache *s)
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 2ef88bbf56a3..9ba59d064b6d 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -6792,14 +6792,12 @@ static int sysfs_slab_add(struct kmem_cache *s)
>>
>> void sysfs_slab_unlink(struct kmem_cache *s)
>> {
>> - if (slab_state >= FULL)
>> - kobject_del(&s->kobj);
>> + kobject_del(&s->kobj);
>> }
>>
>> void sysfs_slab_release(struct kmem_cache *s)
>> {
>> - if (slab_state >= FULL)
>> - kobject_put(&s->kobj);
>> + kobject_put(&s->kobj);
>> }
>>
>> /*