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tun: impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI 

From: "Nathaniel Filardo" <nwfilardo@gmail.com>

Taken from http://bugzilla.kernel.org/show_bug.cgi?id=9806

The TUN/TAP driver only permits one-way transitions of IFF_NO_PI or
IFF_ONE_QUEUE during the lifetime of a tap/tun interface.  Note that
tun_set_iff contains

 541         if (ifr->ifr_flags & IFF_NO_PI)
 542                 tun->flags |= TUN_NO_PI;
 543 
 544         if (ifr->ifr_flags & IFF_ONE_QUEUE)
 545                 tun->flags |= TUN_ONE_QUEUE;

This is easily fixed by adding else branches which clear these bits.

Steps to reproduce:

This is easily reproduced by setting an interface persistant using tunctl then
attempting to open it as IFF_TAP or IFF_TUN, without asserting the IFF_NO_PI
flag.  The ioctl() will succeed and the ifr.flags word is not modified, but the
interface remains in IFF_NO_PI mode (as it was set by tunctl).

Acked-by: Maxim Krasnyansky <maxk@qualcomm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nathaniel Filardo 2008-02-05 03:05:07 -08:00 committed by David S. Miller
parent cd8d627a6b
commit a26af1e08a
1 changed files with 4 additions and 0 deletions
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4
drivers/net/tun.c
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@ -529,9 +529,13 @@ static int tun_set_iff(struct file *file, struct ifreq *ifr)
if (ifr->ifr_flags & IFF_NO_PI)
tun->flags |= TUN_NO_PI;
else
tun->flags &= ~TUN_NO_PI;
if (ifr->ifr_flags & IFF_ONE_QUEUE)
tun->flags |= TUN_ONE_QUEUE;
else
tun->flags &= ~TUN_ONE_QUEUE;
file->private_data = tun;
tun->attached = 1;