linux-kernel - [PATCH] mm/slab: Fix a kmemleak in kmem_cache

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Date: Wed, 28 Feb 2024 11:04:08 +0800
From: Xiaolei Wang <xiaolei.wang@...driver.com>
To: cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/slab: Fix a kmemleak in kmem_cache_destroy()

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:

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@...driver.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);
 }
 
 /*
-- 
2.25.1