oops when propagating mounts into containers - RIP: 0010:[<ffffffff8123cb3e>] [<ffffffff8123cb3e>] propagate_one+0xbe/0x1c0

[Tycho Andersen]

SRU Justification:

Impact: Propagation to some mount tree configurations can cause the kernel to oops. This is trivially reproducible using lxd.

Fix: Upstream cherry pick.

Regression Potential: Both Eric and I have tested the fix and believe that the post-fix code will handle all cases the same as before except for the ones which weren't being handled correctly. I believe the regression potential is small.

---

If I use LXD on xenial with a configuration that does something like: (/nfs in my case is an nfs mount, but based on the kernel code in question anything is probably okay):

devices:
  bind:
    type: disk
    source: /nfs
    path: /nfs
    recursive: "true"

and then start the container and on the host, do a new mount:

sudo mount $ipaddr:/some/nfs/path /nfs/newpath

You get the following kernel oops:

Apr 11 21:59:36 stock2 kernel: [ 1648.993034] Oops: 0000 [#1] SMP
Apr 11 21:59:36 stock2 kernel: [ 1648.993415] Modules linked in: binfmt_misc veth rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache xt_CHECKSUM iptable_mangle xt_tcpudp ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack bridge stp llc iptable_filter ip_tables x_tables zfs(PO) zunicode(PO) zcommon(PO) znvpair(PO) spl(O) zavl(PO) ppdev kvm_intel parport_pc joydev kvm input_leds mac_hid irqbypass parport i2c_piix4 8250_fintek serio_raw ib_iser rdma_cm iw_cm ib_cm ib_sa ib_mad ib_core ib_addr sunrpc iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear cirrus ttm drm_kms_helper syscopyarea sysfillrect sysimgblt psmouse fb_sys_fops floppy drm pata_acpi
Apr 11 21:59:36 stock2 kernel: [ 1649.002015] CPU: 2 PID: 9449 Comm: mount.nfs Tainted: P O 4.4.0-18-generic #34+tych0201604111025
Apr 11 21:59:36 stock2 kernel: [ 1649.003037] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Apr 11 21:59:36 stock2 kernel: [ 1649.004042] task: ffff880074c1a580 ti: ffff880067d30000 task.ti: ffff880067d30000
Apr 11 21:59:36 stock2 kernel: [ 1649.004810] RIP: 0010:[<ffffffff8123cb3e>] [<ffffffff8123cb3e>] propagate_one+0xbe/0x1c0
Apr 11 21:59:36 stock2 kernel: [ 1649.005654] RSP: 0018:ffff880067d33d68 EFLAGS: 00010297
Apr 11 21:59:36 stock2 kernel: [ 1649.006211] RAX: ffff88003bb4ca80 RBX: ffff880074ad8300 RCX: ffff880074503500
Apr 11 21:59:36 stock2 kernel: [ 1649.006934] RDX: 0000000000000000 RSI: 000000000000019c RDI: 0000000000000000
Apr 11 21:59:36 stock2 kernel: [ 1649.007656] RBP: ffff880067d33d78 R08: ffff8800363bad80 R09: ffffffff813eac5c
Apr 11 21:59:36 stock2 kernel: [ 1649.008390] R10: ffffea00002b5800 R11: 0000000000018711 R12: ffff8800363ba600
Apr 11 21:59:36 stock2 kernel: [ 1649.009111] R13: ffff880067d33dc0 R14: ffff880074ad8300 R15: 0000000000000000
Apr 11 21:59:36 stock2 kernel: [ 1649.009835] FS: 00007f653eac4880(0000) GS:ffff88007cd00000(0000) knlGS:0000000000000000
Apr 11 21:59:36 stock2 kernel: [ 1649.010642] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
Apr 11 21:59:36 stock2 kernel: [ 1649.011237] CR2: 0000000000000010 CR3: 0000000077a4e000 CR4: 00000000000006e0
Apr 11 21:59:36 stock2 kernel: [ 1649.011984] Stack:
Apr 11 21:59:36 stock2 kernel: [ 1649.012255] ffff880074ad8300 ffff8800363ba600 ffff880067d33db0 ffffffff8123d060
Apr 11 21:59:36 stock2 kernel: [ 1649.013070] ffff88003bb4ca80 ffff8800363ba600 ffff88000c211980 0000000000000000
Apr 11 21:59:36 stock2 kernel: [ 1649.013892] ffff880067d33e98 ffff880067d33df8 ffffffff8122dd97 ffff88003bb4c900
Apr 11 21:59:36 stock2 kernel: [ 1649.014751] Call Trace:
Apr 11 21:59:36 stock2 kernel: [ 1649.015053] [<ffffffff8123d060>] propagate_mnt+0x120/0x150
Apr 11 21:59:36 stock2 kernel: [ 1649.015643] [<ffffffff8122dd97>] attach_recursive_mnt+0x147/0x230
Apr 11 21:59:36 stock2 kernel: [ 1649.016286] [<ffffffff8122ded8>] graft_tree+0x58/0x90
Apr 11 21:59:36 stock2 kernel: [ 1649.016809] [<ffffffff8122df9e>] do_add_mount+0x8e/0xd0
Apr 11 21:59:36 stock2 kernel: [ 1649.017342] [<ffffffff8122ed70>] do_mount+0x2c0/0xe00
Apr 11 21:59:36 stock2 kernel: [ 1649.017863] [<ffffffff8122e924>] ? copy_mount_options+0xb4/0x220
Apr 11 21:59:36 stock2 kernel: [ 1649.018466] [<ffffffff8122fbdf>] SyS_mount+0x9f/0x100
Apr 11 21:59:36 stock2 kernel: [ 1649.018996] [<ffffffff818243b2>] entry_SYSCALL_64_fastpath+0x16/0x71
Apr 11 21:59:36 stock2 kernel: [ 1649.019631] Code: 39 90 d8 00 00 00 75 ec 8b b0 10 01 00 00 48 89 3d 80 e1 f8 00 48 89 05 81 e1 f8 00 39 b1 10 01 00 00 74 19 48 8b bf d8 00 00 00 <48> 8b 47 10 48 89 3d 5f e1 f8 00 48 89 05 60 e1 f8 00 8b 43 30
Apr 11 21:59:36 stock2 kernel: [ 1649.022395] RIP [<ffffffff8123cb3e>] propagate_one+0xbe/0x1c0
Apr 11 21:59:36 stock2 kernel: [ 1649.022990] RSP <ffff880067d33d68>
Apr 11 21:59:36 stock2 kernel: [ 1649.023362] CR2: 0000000000000010
Apr 11 21:59:36 stock2 kernel: [ 1649.027053] ---[ end trace 46ce79a38cba28a5 ]---

[Seth Forshee (sforshee)]

This doesn't have to be an nfs mount, I've been able to reproduce it using an ext4 loopback mount.

[fcole90 (fcole90)]

Hi, I'm having a kernel oops with similar trace, but for me it happens at login time. Maybe there's an automatic mount.
Mine is https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1578325

[Seth Forshee (sforshee)]

Fix sent to Linus:

http://<email address hidden>

I've tested this on xenial and it fixes the oops. I'll send out patches shortly.

[Kamal Mostafa (kamalmostafa)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-trusty' to 'verification-done-trusty'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Kamal Mostafa (kamalmostafa)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-vivid' to 'verification-done-vivid'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Kamal Mostafa (kamalmostafa)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-wily' to 'verification-done-wily'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Kamal Mostafa (kamalmostafa)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-xenial' to 'verification-done-xenial'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Seth Forshee (sforshee)]

Verified that the problem is fixed in all four kernels.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.4.0-23.41

---------------
linux (4.4.0-23.41) xenial; urgency=low

  [ Kamal Mostafa ]

  * Release Tracking Bug
    - LP: #1582431

  * zfs: disable module checks for zfs when cross-compiling (LP: #1581127)
    - [Packaging] disable zfs module checks when cross-compiling

  * Xenial update to v4.4.10 stable release (LP: #1580754)
    - Revert "UBUNTU: SAUCE: (no-up) ACPICA: Dispatcher: Update thread ID for
      recursive method calls"
    - Revert "UBUNTU: SAUCE: nbd: ratelimit error msgs after socket close"
    - Revert: "powerpc/tm: Check for already reclaimed tasks"
    - RDMA/iw_cxgb4: Fix bar2 virt addr calculation for T4 chips
    - ipvs: handle ip_vs_fill_iph_skb_off failure
    - ipvs: correct initial offset of Call-ID header search in SIP persistence
      engine
    - ipvs: drop first packet to redirect conntrack
    - mfd: intel-lpss: Remove clock tree on error path
    - nbd: ratelimit error msgs after socket close
    - ata: ahci_xgene: dereferencing uninitialized pointer in probe
    - mwifiex: fix corner case association failure
    - CNS3xxx: Fix PCI cns3xxx_write_config()
    - clk-divider: make sure read-only dividers do not write to their register
    - soc: rockchip: power-domain: fix err handle while probing
    - clk: rockchip: free memory in error cases when registering clock branches
    - clk: meson: Fix meson_clk_register_clks() signature type mismatch
    - clk: qcom: msm8960: fix ce3_core clk enable register
    - clk: versatile: sp810: support reentrance
    - clk: qcom: msm8960: Fix ce3_src register offset
    - lpfc: fix misleading indentation
    - ath9k: ar5008_hw_cmn_spur_mitigate: add missing mask_m & mask_p
      initialisation
    - mac80211: fix statistics leak if dev_alloc_name() fails
    - tracing: Don't display trigger file for events that can't be enabled
    - MD: make bio mergeable
    - Minimal fix-up of bad hashing behavior of hash_64()
    - mm, cma: prevent nr_isolated_* counters from going negative
    - mm/zswap: provide unique zpool name
    - ARM: EXYNOS: Properly skip unitialized parent clock in power domain on
    - ARM: SoCFPGA: Fix secondary CPU startup in thumb2 kernel
    - xen: Fix page <-> pfn conversion on 32 bit systems
    - xen/balloon: Fix crash when ballooning on x86 32 bit PAE
    - xen/evtchn: fix ring resize when binding new events
    - HID: wacom: Add support for DTK-1651
    - HID: Fix boot delay for Creative SB Omni Surround 5.1 with quirk
    - Input: zforce_ts - fix dual touch recognition
    - proc: prevent accessing /proc/<PID>/environ until it's ready
    - mm: update min_free_kbytes from khugepaged after core initialization
    - batman-adv: fix DAT candidate selection (must use vid)
    - batman-adv: Check skb size before using encapsulated ETH+VLAN header
    - batman-adv: Fix broadcast/ogm queue limit on a removed interface
    - batman-adv: Reduce refcnt of removed router when updating route
    - writeback: Fix performance regression in wb_over_bg_thresh()
    - MAINTAINERS: Remove asterisk from EFI directory names
    - x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO
    - ARM: cpuidle: Pass on arm_cpuidle_s...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.13.0-87.133

---------------
linux (3.13.0-87.133) trusty; urgency=low

  [ Kamal Mostafa ]

  * Release Tracking Bug
    - LP: #1585315

  [ Upstream Kernel Changes ]

  * Revert "usb: hub: do not clear BOS field during reset device"
    - LP: #1582864

linux (3.13.0-87.132) trusty; urgency=low

  [ Kamal Mostafa ]

  * Release Tracking Bug
    - LP: #1582398

  [ Kamal Mostafa ]

  * [Config] Drop ozwpan from the ABI

  [ Luis Henriques ]

  * [Config] CONFIG_USB_WPAN_HCD=n
    - LP: #1463740
    - CVE-2015-4004

  [ Prarit Bhargava ]

  * SAUCE: (no-up) ACPICA: Dispatcher: Update thread ID for recursive
    method calls
    - LP: #1577898

  [ Upstream Kernel Changes ]

  * usbnet: cleanup after bind() in probe()
    - LP: #1567191
    - CVE-2016-3951
  * KVM: x86: bit-ops emulation ignores offset on 64-bit
    - LP: #1423672
  * USB: usbip: fix potential out-of-bounds write
    - LP: #1572666
    - CVE-2016-3955
  * x86/mm/32: Enable full randomization on i386 and X86_32
    - LP: #1568523
    - CVE-2016-3672
  * Input: gtco - fix crash on detecting device without endpoints
    - LP: #1575706
    - CVE-2016-2187
  * atl2: Disable unimplemented scatter/gather feature
    - LP: #1561403
    - CVE-2016-2117
  * ALSA: usb-audio: Skip volume controls triggers hangup on Dell USB Dock
    - LP: #1577905
  * fs/pnode.c: treat zero mnt_group_id-s as unequal
    - LP: #1572316
  * propogate_mnt: Handle the first propogated copy being a slave
    - LP: #1572316
  * drm: Balance error path for GEM handle allocation
    - LP: #1579610
  * x86/mm: Add barriers and document switch_mm()-vs-flush synchronization
    - LP: #1538429
    - CVE-2016-2069
  * x86/mm: Improve switch_mm() barrier comments
    - LP: #1538429
    - CVE-2016-2069
  * net: fix infoleak in llc
    - LP: #1578496
    - CVE-2016-4485
  * net: fix infoleak in rtnetlink
    - LP: #1578497
    - CVE-2016-4486

 -- Kamal Mostafa <email address hidden> Tue, 24 May 2016 11:04:30 -0700

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-lts-utopic - 3.16.0-73.95~14.04.1

---------------
linux-lts-utopic (3.16.0-73.95~14.04.1) trusty; urgency=low

  [ Kamal Mostafa ]

  * CVE-2016-1583 (LP: #1588871)
    - ecryptfs: fix handling of directory opening
    - SAUCE: proc: prevent stacking filesystems on top
    - SAUCE: ecryptfs: forbid opening files without mmap handler

 -- Andy Whitcroft <email address hidden> Thu, 09 Jun 2016 08:46:24 +0100

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.19.0-61.69

---------------
linux (3.19.0-61.69) vivid; urgency=low

  [ Kamal Mostafa ]

  * CVE-2016-1583 (LP: #1588871)
    - ecryptfs: fix handling of directory opening
    - SAUCE: proc: prevent stacking filesystems on top
    - SAUCE: ecryptfs: forbid opening files without mmap handler
    - SAUCE: sched: panic on corrupted stack end

 -- Andy Whitcroft <email address hidden> Wed, 08 Jun 2016 22:25:58 +0100

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.2.0-38.45

---------------
linux (4.2.0-38.45) wily; urgency=low

  [ Kamal Mostafa ]

  * CVE-2016-1583 (LP: #1588871)
    - ecryptfs: fix handling of directory opening
    - SAUCE: proc: prevent stacking filesystems on top
    - SAUCE: ecryptfs: forbid opening files without mmap handler
    - SAUCE: sched: panic on corrupted stack end

 -- Andy Whitcroft <email address hidden> Wed, 08 Jun 2016 22:10:39 +0100

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.4.0-24.43

---------------
linux (4.4.0-24.43) xenial; urgency=low

  [ Kamal Mostafa ]

  * CVE-2016-1583 (LP: #1588871)
    - ecryptfs: fix handling of directory opening
    - SAUCE: proc: prevent stacking filesystems on top
    - SAUCE: ecryptfs: forbid opening files without mmap handler
    - SAUCE: sched: panic on corrupted stack end

  * arm64: statically link rtc-efi (LP: #1583738)
    - [Config] Link rtc-efi statically on arm64

 -- Kamal Mostafa <email address hidden> Fri, 03 Jun 2016 10:02:16 -0700