linux-kernel - Re: tun: memory leak in tun_set

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Date:   Wed, 17 Jan 2018 19:44:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xin Long <lucien.xin@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: tun: memory leak in tun_set_iff



On 2018年01月17日 19:07, Xin Long wrote:
> On Wed, Jan 10, 2018 at 2:20 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> Hello,
>>
>> syzkaller has hit the following memory leak on 4.15-rc7.
>> Reproducer is attached.
>>
>> unreeferenced object 0xffff88002c9ac400 (size 4096):
>>    comm "syz-executor0", pid 12349, jiffies 4295751114 (age 10.067s)
>>    hex dump (first 32 bytes):
>>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>    backtrace:
>>      [<00000000ad172f4e>] kmemleak_alloc_recursive
>> include/linux/kmemleak.h:55 [inline]
>>      [<00000000ad172f4e>] slab_post_alloc_hook mm/slab.h:440 [inline]
>>      [<00000000ad172f4e>] slab_alloc_node mm/slub.c:2725 [inline]
>>      [<00000000ad172f4e>] slab_alloc mm/slub.c:2733 [inline]
>>      [<00000000ad172f4e>] __kmalloc+0x1a9/0x340 mm/slub.c:3758
>>      [<00000000d66b86d6>] kmalloc_array include/linux/slab.h:618 [inline]
>>      [<00000000d66b86d6>] kcalloc include/linux/slab.h:629 [inline]
>>      [<00000000d66b86d6>] __ptr_ring_init_queue_alloc
>> include/linux/ptr_ring.h:450 [inline]
>>      [<00000000d66b86d6>] ptr_ring_init include/linux/ptr_ring.h:468 [inline]
>>      [<00000000d66b86d6>] skb_array_init include/linux/skb_array.h:176 [inline]
>>      [<00000000d66b86d6>] tun_attach+0x940/0x10b0 drivers/net/tun.c:754
>>      [<000000007a69e5cb>] tun_set_iff drivers/net/tun.c:2315 [inline]
>>      [<000000007a69e5cb>] __tun_chr_ioctl+0x2435/0x4210 drivers/net/tun.c:2524
>>      [<000000005c75f6a6>] tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2773
>>      [<00000000ece2f188>] vfs_ioctl fs/ioctl.c:46 [inline]
>>      [<00000000ece2f188>] file_ioctl fs/ioctl.c:500 [inline]
>>      [<00000000ece2f188>] do_vfs_ioctl+0x1cf/0x16b0 fs/ioctl.c:684
>>      [<0000000021f4fda7>] SYSC_ioctl fs/ioctl.c:701 [inline]
>>      [<0000000021f4fda7>] SyS_ioctl+0xb6/0xe0 fs/ioctl.c:692
>>      [<0000000001148918>] entry_SYSCALL_64_fastpath+0x23/0x9a
>>      [<000000008d0cf26e>] 0xffffffffffffffff
> we probably just need:
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -831,8 +831,10 @@ static int tun_attach(struct tun_struct *tun,
> struct file *file,
>                  /* Setup XDP RX-queue info, for new tfile getting attached */
>                  err = xdp_rxq_info_reg(&tfile->xdp_rxq,
>                                         tun->dev, tfile->queue_index);
> -               if (err < 0)
> +               if (err < 0) {
> +                       ptr_ring_cleanup(&tfile->tx_ring, NULL);
>                          goto out;
> +               }
>
> will check it for sure.

Good catch. This looks like a new bug in net-next instead of the what 
memory leaker told us here.

Wang Cong has posted a possible fix for this.

Thanks