netdev - Re: 4.4.103 linux kernel regression

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Date:   Sun, 24 Dec 2017 12:25:22 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Mathias Tillman <master.homer@...il.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, netdev@...r.kernel.org,
        stable@...r.kernel.org, xiyou.wangcong@...il.com,
        dsahern@...il.com, jeffy.chen@...k-chips.com, davem@...emloft.net
Subject: Re: 4.4.103 linux kernel regression

On 23.12.2017 21:10, Mathias Tillman wrote:
> Thank you, I will test that patch and see if I can find anything interesting in the log. Will have to be some time later next week due to 
> the holidays, but I will get back to you with the results.

Ok, I'll be waiting.

Probably you could share your kernel config and lsmod output?

> 
> What commit are you referring to exactly? I can test it to see if it's fixed.

Commit that was added into v4.4.103 - 76da0704507bbc51875013f6557877ab308cfd0a upstream.

> 
> Also, I should mention that it's not just vsftpd it causes problems with - some other people have reported problems with starting and 
> stopping lxc containers. I don't use those myself so I can't really comment on that, but it does seem to have been fixed by reverting the 
> commit I mentioned.

Yes. This is common problem for all network namespaces.
Bug somewhere else and requires particular configuration.

> 
> Greg: Can't say if the problem exists on master or not - I'm really only able to reproduce it on the Turris Omnia router as I said in the 
> bug report. It's based on openwrt and requires some device-specific patches to function properly, so I'm not sure it would work on the 
> latest - but I can give it a try.
> 
> Regards
> Mathias
> 
> 
> On Sat, 23 Dec 2017, 17:36 Konstantin Khlebnikov, <khlebnikov@...dex-team.ru <mailto:khlebnikov@...dex-team.ru>> wrote:
> 
>     On 23.12.2017 16:52, Greg KH wrote:
>      > adding stable@ and netdev@
>      >
>      > On Sat, Dec 23, 2017 at 10:49:27AM +0000, Mathias Tillman wrote:
>      >> Hi, I wanted to make you aware of a recent regression to the Linux kernel
>      >> introduced with commit 2417da3f4d6bc4fc6c77f613f0e2264090892aa5:
>      >>
>     https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/net/ipv6?h=linux-4.4.y&id=2417da3f4d6bc4fc6c77f613f0e2264090892aa5
>      >
>      > Is this issue also present in Linus's tree?
>      >
>      >> I have reported it here:
>      >> https://bugzilla.kernel.org/show_bug.cgi?id=198189
>      >
>      > Bugzilla doesn't work for networking bugs, nor stable stuff, just for a
>      > few subsystems, sorry.
>      >
>      >> Basically, that commit causes an endless loop if, for some reason, not all
>      >> devices are unregistered in the rollback_registered_many function in
>      >> net/dev.c
>      >>
>      >> Decided to contact you directly since I have yet to receive any reply on
>      >> the bug report, and I wasn't entirely sure what the procedure was. Please
>      >> do let me know if I have to change anything in the report.
>      >
>      > I can revert it, but it would be good to verify if this is an issue in
>      > the latest releases or not first.
> 
>     Most likely bug fixed by that commit hid refcount leak for loopback device.
> 
>     Mathias, please try debug patch from attachment.
>     It logs all refcount changes for loopback in non-host net namespace.
>     Hopefully log would will be tiny and show what is missing.
> 
>     Looks like vsftpd creates and destroys empty net-ns, like "unshare -n true"
>