Re: [libvirt] [PATCH v2] util: netdevbridge: fall back to ioctl from sysfs

[Christian Ehrhardt]

On Sun, Nov 25, 2018 at 10:01 PM Laine Stump  wrote:

> On 11/23/18 1:42 AM, Christian Ehrhardt wrote:
>
>
>
> On Tue, Nov 20, 2018 at 1:26 PM Daniel P. Berrangé 
> wrote:
>
>> On Tue, Nov 20, 2018 at 01:25:46PM +0100, Christian Ehrhardt wrote:
>> > There are certain cases e.g. containers where the sysfs path might
>> > exists, but might fail. Unfortunately the exact restrictions are only
>> > known to libvirt when trying to write to it so we need to try it.
>> >
>> > But in case it fails there is no need to fully abort, in those cases try
>> > to fall back to the older ioctl interface which can still work.
>> >
>> > That makes setting up a bridge in unprivileged LXD containers work.
>> >
>> > Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1802906
>> >
>> > Signed-off-by: Christian Ehrhardt 
>> > Reported-by: Brian Candler 
>> > ---
>> >  src/util/virnetdevbridge.c | 48 +-
>> >  1 file changed, 26 insertions(+), 22 deletions(-)
>>
>> Reviewed-by: Daniel P. Berrangé 
>>
>
> Thanks for the review Daniel!
>
> Brian (on CC) also tested a Ubuntu build with the fix applied and it
> worked for him in unprivileged containers.
>
> There was no other feedback in the last three days.
> But this is no area I feel entitled to push the change on my own,
> therefore I wanted to ping on this - ping
>
>
> As long as you have commit privileges, feel free to push once there is a
> Reviewed-by: (unless we are in freeze).
>
 I wanted to be better safe than sorry, thanks for the confirmation.

> If it makes you feel any more confident about pushing - I had personally
> expressed misgivings about this patch in IRC to Dan because on first read
> it sounded like we might be exploiting a security flaw in LXC to modify
> networking when it shouldn't actually be allowed, but he convinced me that
> the situation isn't that "bridge and tap device management via sysfs is
> blocked because it should be, and ioctls are accidentally left enabled when
> they should have been disabled", but rather that "bridge/tap device
> management is acceptable in this situation, but sysfs is a huge can of
> worms that can only be made read-only on a global basis (and *must* be made
> read-only due to all the other things that shouldn't be allowed in this
> case)". Based on that, I'm okay with the patch as well.
>
> Ack to the can-of-worms being the reason :-)
Thanks !

... pushed to master now
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Re: [libvirt] [PATCH v2] util: netdevbridge: fall back to ioctl from sysfs

[Laine Stump]

On 11/23/18 1:42 AM, Christian Ehrhardt wrote:
>
>
> On Tue, Nov 20, 2018 at 1:26 PM Daniel P. Berrangé
> mailto:berra...@redhat.com>> wrote:
>
> On Tue, Nov 20, 2018 at 01:25:46PM +0100, Christian Ehrhardt wrote:
> > There are certain cases e.g. containers where the sysfs path might
> > exists, but might fail. Unfortunately the exact restrictions are
> only
> > known to libvirt when trying to write to it so we need to try it.
> >
> > But in case it fails there is no need to fully abort, in those
> cases try
> > to fall back to the older ioctl interface which can still work.
> >
> > That makes setting up a bridge in unprivileged LXD containers work.
> >
> > Fixes:
> https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1802906
> >
> > Signed-off-by: Christian Ehrhardt
>  >
> > Reported-by: Brian Candler  >
> > ---
> >  src/util/virnetdevbridge.c | 48
> +-
> >  1 file changed, 26 insertions(+), 22 deletions(-)
>
> Reviewed-by: Daniel P. Berrangé  >
>
>
> Thanks for the review Daniel!
>
> Brian (on CC) also tested a Ubuntu build with the fix applied and it
> worked for him in unprivileged containers.
>
> There was no other feedback in the last three days.
> But this is no area I feel entitled to push the change on my own,
> therefore I wanted to ping on this - ping


As long as you have commit privileges, feel free to push once there is a
Reviewed-by: (unless we are in freeze).


If it makes you feel any more confident about pushing - I had personally
expressed misgivings about this patch in IRC to Dan because on first
read it sounded like we might be exploiting a security flaw in LXC to
modify networking when it shouldn't actually be allowed, but he
convinced me that the situation isn't that "bridge and tap device
management via sysfs is blocked because it should be, and ioctls are
accidentally left enabled when they should have been disabled", but
rather that "bridge/tap device management is acceptable in this
situation, but sysfs is a huge can of worms that can only be made
read-only on a global basis (and *must* be made read-only due to all the
other things that shouldn't be allowed in this case)". Based on that,
I'm okay with the patch as well.

 


>
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Re: [libvirt] [PATCH v2] util: netdevbridge: fall back to ioctl from sysfs

[Christian Ehrhardt]

On Tue, Nov 20, 2018 at 1:26 PM Daniel P. Berrangé 
wrote:

> On Tue, Nov 20, 2018 at 01:25:46PM +0100, Christian Ehrhardt wrote:
> > There are certain cases e.g. containers where the sysfs path might
> > exists, but might fail. Unfortunately the exact restrictions are only
> > known to libvirt when trying to write to it so we need to try it.
> >
> > But in case it fails there is no need to fully abort, in those cases try
> > to fall back to the older ioctl interface which can still work.
> >
> > That makes setting up a bridge in unprivileged LXD containers work.
> >
> > Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1802906
> >
> > Signed-off-by: Christian Ehrhardt 
> > Reported-by: Brian Candler 
> > ---
> >  src/util/virnetdevbridge.c | 48 +-
> >  1 file changed, 26 insertions(+), 22 deletions(-)
>
> Reviewed-by: Daniel P. Berrangé 
>

Thanks for the review Daniel!

Brian (on CC) also tested a Ubuntu build with the fix applied and it worked
for him in unprivileged containers.

There was no other feedback in the last three days.
But this is no area I feel entitled to push the change on my own, therefore
I wanted to ping on this - ping
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Re: [libvirt] [PATCH v2] util: netdevbridge: fall back to ioctl from sysfs

[Daniel P . Berrangé]

On Tue, Nov 20, 2018 at 01:25:46PM +0100, Christian Ehrhardt wrote:
> There are certain cases e.g. containers where the sysfs path might
> exists, but might fail. Unfortunately the exact restrictions are only
> known to libvirt when trying to write to it so we need to try it.
> 
> But in case it fails there is no need to fully abort, in those cases try
> to fall back to the older ioctl interface which can still work.
> 
> That makes setting up a bridge in unprivileged LXD containers work.
> 
> Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1802906
> 
> Signed-off-by: Christian Ehrhardt 
> Reported-by: Brian Candler 
> ---
>  src/util/virnetdevbridge.c | 48 +-
>  1 file changed, 26 insertions(+), 22 deletions(-)

Reviewed-by: Daniel P. Berrangé 


Regards,
Daniel
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