linux-kernel - Re: [PATCH] nilfs2: fix memory leak in nilfs_sysfs_delete_device

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Date:   Fri, 25 Jun 2021 04:29:22 +0900
From:   Ryusuke Konishi <konishi.ryusuke@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Pavel Skripkin <paskripkin@...il.com>,
        Vyacheslav Dubeyko <Vyacheslav.Dubeyko@...t.com>,
        linux-nilfs <linux-nilfs@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nilfs2: fix memory leak in nilfs_sysfs_delete_device_group

Hi Andrew,

On Sat, Jun 12, 2021 at 11:06 PM Pavel Skripkin <paskripkin@...il.com> wrote:
>
> My local syzbot instance hit memory leak in nilfs2.
> The problem was in missing kobject_put() in
> nilfs_sysfs_delete_device_group().
>
> kobject_del() does not call kobject_cleanup() for
> passed kobject and it leads to leaking duped
> kobject name if kobject_put() was not called.
>
> Fail log:
>
> BUG: memory leak
> unreferenced object 0xffff8880596171e0 (size 8):
>   comm "syz-executor379", pid 8381, jiffies 4294980258 (age 21.100s)
>   hex dump (first 8 bytes):
>     6c 6f 6f 70 30 00 00 00                          loop0...
>   backtrace:
>     [<ffffffff81a2c656>] kstrdup+0x36/0x70 mm/util.c:60
>     [<ffffffff81a2c6e3>] kstrdup_const+0x53/0x80 mm/util.c:83
>     [<ffffffff83ccc698>] kvasprintf_const+0x108/0x190 lib/kasprintf.c:48
>     [<ffffffff83e99926>] kobject_set_name_vargs+0x56/0x150 lib/kobject.c:289
>     [<ffffffff83e99fd9>] kobject_add_varg lib/kobject.c:384 [inline]
>     [<ffffffff83e99fd9>] kobject_init_and_add+0xc9/0x160 lib/kobject.c:473
>     [<ffffffff8304e840>] nilfs_sysfs_create_device_group+0x150/0x800 fs/nilfs2/sysfs.c:999
>     [<ffffffff830159f6>] init_nilfs+0xe26/0x12b0 fs/nilfs2/the_nilfs.c:637
>
> Fixes: da7141fb78db ("nilfs2: add /sys/fs/nilfs2/<device> group")
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>

This fix looks correct to me.

Acked-by: Ryusuke Konishi <konishi.ryusuke@...il.com>

Thanks,
Ryusuke Konishi

> ---
>  fs/nilfs2/sysfs.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
> index 303d71430bdd..9c6c0e2e5880 100644
> --- a/fs/nilfs2/sysfs.c
> +++ b/fs/nilfs2/sysfs.c
> @@ -1053,6 +1053,7 @@ void nilfs_sysfs_delete_device_group(struct the_nilfs *nilfs)
>         nilfs_sysfs_delete_superblock_group(nilfs);
>         nilfs_sysfs_delete_segctor_group(nilfs);
>         kobject_del(&nilfs->ns_dev_kobj);
> +       kobject_put(&nilfs->ns_dev_kobj);
>         kfree(nilfs->ns_dev_subgroups);
>  }
>
> --
> 2.32.0
>