Re: [PATCH] Revert "mm/slub: fix a memory leak in sysfs_slab_add()"
From: Vlastimil Babka <hidden>
Date: 2021-01-28 12:06:06
Also in:
linux-mm, lkml
On 1/28/21 12:32 PM, Wang Hai wrote:
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@syzkaller.appspotmail.com
Fixes: dde3c6b72a16 ("mm/slub: fix a memory leak in sysfs_slab_add()")
Signed-off-by: Wang Hai <redacted>Cc: <redacted> Acked-by: Vlastimil Babka <redacted> Double-free is worse than a rare small memory leak. Which would still be nice to fix, but I'm afraid it will be more complicated, so start with preventing the worse issue, including stable.
quoted hunk ↗ jump to hunk
--- 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)