netdev - [PATCH] Revert "mm/slub: fix a memory leak in sysfs_slab

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Date:   Thu, 28 Jan 2021 19:32:50 +0800
From:   Wang Hai <wanghai38@...wei.com>
To:     <torvalds@...ux-foundation.org>, <cl@...ux.com>,
        <penberg@...nel.org>, <rientjes@...gle.com>,
        <iamjoonsoo.kim@....com>, <akpm@...ux-foundation.org>,
        <vbabka@...e.cz>
CC:     <asmadeus@...ewreck.org>, <davem@...emloft.net>,
        <ericvh@...il.com>, <kuba@...nel.org>, <lucho@...kov.net>,
        <netdev@...r.kernel.org>, <syzkaller-bugs@...glegroups.com>,
        <v9fs-developer@...ts.sourceforge.net>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        <syzbot+d0bd96b4696c1ef67991@...kaller.appspotmail.com>
Subject: [PATCH] Revert "mm/slub: fix a memory leak in sysfs_slab_add()"

This reverts commit dde3c6b72a16c2db826f54b2d49bdea26c3534a2.

syzbot report a double-free bug. The following case can cause this bug.
 - mm/slab_common.c: create_cache(): if the __kmem_cache_create()
fails, it does:

	out_free_cache:
		kmem_cache_free(kmem_cache, s);

 - but __kmem_cache_create() - at least for slub() - will have done

	sysfs_slab_add(s)
		-> sysfs_create_group() .. fails ..
		-> kobject_del(&s->kobj); .. which frees s ...

We can't remove the kmem_cache_free() in create_cache(), because
other error cases of __kmem_cache_create() do not free this.

So, revert the commit dde3c6b72a16 ("mm/slub: fix a memory leak in
sysfs_slab_add()") to fix this.

Reported-by: syzbot+d0bd96b4696c1ef67991@...kaller.appspotmail.com
Fixes: dde3c6b72a16 ("mm/slub: fix a memory leak in sysfs_slab_add()")
Signed-off-by: Wang Hai <wanghai38@...wei.com>
---
 mm/slub.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 69742ab9a21d..7ecbbbe5bc0c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5625,10 +5625,8 @@ static int sysfs_slab_add(struct kmem_cache *s)
 
 	s->kobj.kset = kset;
 	err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
-	if (err) {
-		kobject_put(&s->kobj);
+	if (err)
 		goto out;
-	}
 
 	err = sysfs_create_group(&s->kobj, &slab_attr_group);
 	if (err)
-- 
2.17.1