Re: [PATCH net-next v2] net: openvswitch: fix uAPI incompatibility with existing user space

[Nicolas Dichtel]

Le 09/03/2022 à 23:20, Ilya Maximets a écrit :
> Few years ago OVS user space made a strange choice in the commit [1]
> to define types only valid for the user space inside the copy of a
> kernel uAPI header.  '#ifndef __KERNEL__' and another attribute was
> added later.
> 
> This leads to the inevitable clash between user space and kernel types
> when the kernel uAPI is extended.  The issue was unveiled with the
> addition of a new type for IPv6 extension header in kernel uAPI.
> 
> When kernel provides the OVS_KEY_ATTR_IPV6_EXTHDRS attribute to the
> older user space application, application tries to parse it as
> OVS_KEY_ATTR_PACKET_TYPE and discards the whole netlink message as
> malformed.  Since OVS_KEY_ATTR_IPV6_EXTHDRS is supplied along with
> every IPv6 packet that goes to the user space, IPv6 support is fully
> broken.
> 
> Fixing that by bringing these user space attributes to the kernel
> uAPI to avoid the clash.  Strictly speaking this is not the problem
> of the kernel uAPI, but changing it is the only way to avoid breakage
> of the older user space applications at this point.
> 
> These 2 types are explicitly rejected now since they should not be
> passed to the kernel.  Additionally, OVS_KEY_ATTR_TUNNEL_INFO moved
> out from the '#ifdef __KERNEL__' as there is no good reason to hide
> it from the userspace.  And it's also explicitly rejected now, because
> it's for in-kernel use only.
> 
> Comments with warnings were added to avoid the problem coming back.
> 
> (1 << type) converted to (1ULL << type) to avoid integer overflow on
> OVS_KEY_ATTR_IPV6_EXTHDRS, since it equals 32 now.
> 
>  [1] beb75a40fdc2 ("userspace: Switching of L3 packets in L2 pipeline")
> 
> Fixes: 28a3f0601727 ("net: openvswitch: IPv6: Add IPv6 extension header support")
> Link: https://lore.kernel.org/netdev/3adf00c7-fe65-3ef4-b6d7-6d8a0cad8a5f@xxxxxxxxxx
> Link: https://github.com/openvswitch/ovs/commit/beb75a40fdc295bfd6521b0068b4cd12f6de507c
> Reported-by: Roi Dayan <roid@xxxxxxxxxx>
> Signed-off-by: Ilya Maximets <i.maximets@xxxxxxx>
Thanks for finally doing this. I also suggest it months ago:
https://lore.kernel.org/lkml/a4894aef-b82a-8224-611d-07be229f5ebe@xxxxxxxxx/

Acked-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>