SSH sockets on overlayfs report connection refused

[Alkis Georgopoulos]

Reusing a master ssh socket that is created on an overlayfs mount reports connection refused, while on real filesystems or on tmpfs it works fine.

Steps to reproduce (/var is ext4, /tmp is tmpfs.):
# mkdir -p /var/overlayfs-socket
# cd /var/overlayfs-socket
# mkdir root rofs /tmp/cow
# mount -t overlayfs -o "upperdir=/tmp/cow,lowerdir=rofs" overlayfs root
# ssh -NMS root/socket alkisg@localhost
alkisg@localhost's password: [****]

And on another tab of the same terminal:
# ssh -S root/socket alkisg@localhost ls
Control socket connect(root/socket): Connection refused
alkisg@localhost's password:

The problem is in the last line, on real filesystems or on tmpfs it doesn't ask for a password, it reuses the existing socket.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.12.0-7-generic 3.12.0-7.15
ProcVersionSignature: Ubuntu 3.12.0-7.15-generic 3.12.4
Uname: Linux 3.12.0-7-generic i686
ApportVersion: 2.12.7-0ubuntu2
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: alkisg 3511 F.... pulseaudio
 /dev/snd/controlC0: alkisg 3511 F.... pulseaudio
CurrentDesktop: GNOME
Date: Wed Dec 18 18:57:18 2013
HibernationDevice: RESUME=UUID=5eff7bf1-95b5-4fc1-9c71-0950810c717e
InstallationDate: Installed on 2013-10-31 (48 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release i386 (20131021.1)
MachineType: System manufacturer System Product Name
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.12.0-7-generic root=UUID=e1f06e01-d2dc-45e5-b446-54e1e4a5dc2c ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.12.0-7-generic N/A
 linux-backports-modules-3.12.0-7-generic N/A
 linux-firmware 1.117
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/04/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0415
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: P5KPL-AM EPU
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: x.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0415:bd02/04/2010:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnP5KPL-AMEPU:rvrx.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.13 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.13-rc4-trusty/

[Alkis Georgopoulos (alkisg)]

AFAIK, overlayfs is not mainlined yet.

The problem I reported exists in the Ubuntu patched kernels of at least Precise, Raring and Trusty though.

[Tomasz Cholewa (slashroot)]

Hi guys,

I've been struggling with similar issue in centos 6.6. In previous version (6.5) everything worked fine, but after update I wasn't able to set socket for ssh control master on overlayfs. I made some tedious research and comparisons and it turned out that it's not about the kernel (made few downgrades) but ssh.
According to https://bugzilla.redhat.com/show_bug.cgi?id=953088 in ssh version included in RHEL 6.6 (and CentOS) there was a patch witch modifies behaviour of creating control socket. When I downgraded ssh packages (openssh{,-clients,-server}) to the version without that patch (5.3p1-94.el6) everything worked like a charm!

I hope it will also help you to solve your problem in Ubuntu.