Re: [PATCH 0/5] tun/macvtap: TUNSETIFF fixes

[Jason Wang]

On Tue, Dec 16, 2014 at 9:04 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> 
wrote:
> Dan Carpenter reported the following:
> 	static checker warning:
>
> 		drivers/net/tun.c:1694 tun_set_iff()
> 		warn: 0x17100 is larger than 16 bits
>
> 	drivers/net/tun.c
> 	  1692
> 	  1693          tun->flags = (tun->flags & ~TUN_FEATURES) |
> 	  1694                  (ifr->ifr_flags & TUN_FEATURES);
> 	  1695
>
> 	It's complaining because the "ifr->ifr_flags" variable is a short
> 	(should it be unsigned?).  The new define:
>
> 	#define IFF_VNET_LE    0x10000
>
> 	doesn't fit in two bytes.  Other suspect looking code could be:
>
> 		return __virtio16_to_cpu(q->flags & IFF_VNET_LE, val);
>
> And that's true: we have run out of IFF flags in tun.

I don't have objections on this series.
Just note that we still have several bits available.
> So let's not try to add more: add simple GET/SET ioctls
> instead. Easy to test, leads to clear semantics.
>
> Alternatively we'll have to revert the whole thing for 3.19,
> but that seems more work as this has dependencies
> in other places.
>
> While here, I noticed that macvtap was actually reading
> ifreq flags as a 32 bit field.
> Fix that up as well.
>
> Michael S. Tsirkin (5):
>   macvtap: fix uninitialized access on TUNSETIFF
>   if_tun: add TUNSETVNETLE/TUNGETVNETLE
>   tun: drop broken IFF_VNET_LE
>   macvtap: drop broken IFF_VNET_LE
>   if_tun: drop broken IFF_VNET_LE
>
>  include/uapi/linux/if_tun.h |  3 ++-
>  drivers/net/macvtap.c       | 30 ++++++++++++++++++++++++------
>  drivers/net/tun.c           | 26 +++++++++++++++++++++++---
>  3 files changed, 49 insertions(+), 10 deletions(-)
>
> --
> MST
>
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