[ovs-dev] [PATCH V3 06/24] datapath: fix GFP flags in rtnl_net_notifyid()

[Yi-Hung Wei]

On Wed, Sep 16, 2020 at 10:34 AM Greg Rose <gvrose8192 at gmail.com> wrote:
>
> From: Guillaume Nault <gnault at redhat.com>
>
> Upstream commit:
>     commit d4e4fdf9e4a27c87edb79b1478955075be141f67
>     Author: Guillaume Nault <gnault at redhat.com>
>     Date:   Wed Oct 23 18:39:04 2019 +0200
>
>     netns: fix GFP flags in rtnl_net_notifyid()
>
>     In rtnl_net_notifyid(), we certainly can't pass a null GFP flag to
>     rtnl_notify(). A GFP_KERNEL flag would be fine in most circumstances,
>     but there are a few paths calling rtnl_net_notifyid() from atomic
>     context or from RCU critical sections. The later also precludes the use
>     of gfp_any() as it wouldn't detect the RCU case. Also, the nlmsg_new()
>     call is wrong too, as it uses GFP_KERNEL unconditionally.
>
>     Therefore, we need to pass the GFP flags as parameter and propagate it
>     through function calls until the proper flags can be determined.
>
>     In most cases, GFP_KERNEL is fine. The exceptions are:
>       * openvswitch: ovs_vport_cmd_get() and ovs_vport_cmd_dump()
>         indirectly call rtnl_net_notifyid() from RCU critical section,
>
>       * rtnetlink: rtmsg_ifinfo_build_skb() already receives GFP flags as
>         parameter.
>
>     Also, in ovs_vport_cmd_build_info(), let's change the GFP flags used
>     by nlmsg_new(). The function is allowed to sleep, so better make the
>     flags consistent with the ones used in the following
>     ovs_vport_cmd_fill_info() call.
>
>     Found by code inspection.
>
>     Fixes: 9a9634545c70 ("netns: notify netns id events")
>     Signed-off-by: Guillaume Nault <gnault at redhat.com>
>     Acked-by: Nicolas Dichtel <nicolas.dichtel at 6wind.com>
>     Acked-by: Pravin B Shelar <pshelar at ovn.org>
>     Signed-off-by: David S. Miller <davem at davemloft.net>
>
> Backport the datapath.c portion of this fix.
>
> Cc:  Guillaume Nault <gnault at redhat.com>
> Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
> ---

LGTM.

Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>