Re: [RFC PATCH] tun: don't zeroize sock->file on detach

[Yuchung Cheng]

On Wed, Aug 8, 2012 at 5:53 AM, Stanislav Kinsbursky
<skinsbursky@xxxxxxxxxxxxx> wrote:
> Hi, Dave.
> What about this patch?
>
>
> On Wed, Jul 11, 2012 at 03:48:20PM +0400, Stanislav Kinsbursky wrote:
>>
>> This is a fix for bug, introduced in 3.4 kernel by commit
>> 1ab5ecb90cb6a3df1476e052f76a6e8f6511cb3d, which, among other things,
>> replaced
>> simple sock_put() by sk_release_kernel(). Below is sequence, which leads
>> to
>> oops for non-persistent devices:
>>
>> tun_chr_close()
>> tun_detach()                            <== tun->socket.file = NULL
>> tun_free_netdev()
>> sk_release_sock()
>> sock_release(sock->file == NULL)
>> iput(SOCK_INODE(sock))                  <== dereference on NULL pointer
>>
>> This patch just removes zeroing of socket's file from __tun_detach().
>> sock_release() will do this.
>>
>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Acked-by: Yuchung Cheng <ycheng@xxxxxxxxxx>

I has tested this patch and it works (so my kernel stops crashing
using tun devices).

>> ---
>>  drivers/net/tun.c |    1 -
>>  1 files changed, 0 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index 987aeef..c1639f3 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -185,7 +185,6 @@ static void __tun_detach(struct tun_struct *tun)
>>         netif_tx_lock_bh(tun->dev);
>>         netif_carrier_off(tun->dev);
>>         tun->tfile = NULL;
>> -       tun->socket.file = NULL;
>>         netif_tx_unlock_bh(tun->dev);
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/