[trusty] btrfs kernel NULL pointer dereference while exercising test for commit 0aeb8a6e67cddeac1d42cf64795fde0641a1cffb

SRU Justification:

[Impact]
Running a btrfs test I trip a NULL pointer dereference

[Fix]
clean upstream cherry pick 755f780865221252ef3321215c9796b78e7b1c5 ("btrfs: fix null pointer dereference in clone_fs_devices when name is null")

[Testcase]
See attached hacked up bash script.btrfs: Without the fix I can reproduce the oops every time. With the fix, it works perfectly.

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!

verified on -proposed kernel, I don't see the issue

Linux ubuntu 3.13.0-49-generic #81-Ubuntu SMP Tue Mar 24 19:29:48 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

This bug was fixed in the package linux - 3.13.0-49.81

---------------
linux (3.13.0-49.81) trusty; urgency=low

  [ Kamal Mostafa ]

  * Release Tracking Bug
    - LP: #1436016

  [ Alex Hung ]

  * SAUCE: ACPI / blacklist: blacklist Win8 OSI for HP Pavilion dv6
    - LP: #1416940

  [ Andy Whitcroft ]

  * [Packaging] generate live watchdog blacklists
    - LP: #1432837

  [ Ben Widawsky ]

  * SAUCE: i915_bdw: drm/i915/bdw: enable eDRAM.
    - LP: #1430855

  [ Chris J Arges ]

  * [Config] Add ibmvfc to d-i
    - LP: #1416001

  [ Seth Forshee ]

  * [Config] updateconfigs - enable X86_UP_APIC_MSI

  [ Upstream Kernel Changes ]

  * net: add sysfs helpers for netdev_adjacent logic
    - LP: #1410852
  * net: Mark functions as static in core/dev.c
    - LP: #1410852
  * net: rename sysfs symlinks on device name change
    - LP: #1410852
  * btrfs: fix null pointer dereference in clone_fs_devices when name is
    null
    - LP: #1429804
  * cdc-acm: add sanity checks
    - LP: #1413992
  * x86: thinkpad_acpi.c: fixed spacing coding style issue
    - LP: #1417915
  * thinkpad_acpi: support new BIOS version string pattern
    - LP: #1417915
  * net: sctp: fix slab corruption from use after free on INIT collisions
    - LP: #1416506
    - CVE-2015-1421
  * ipv4: try to cache dst_entries which would cause a redirect
    - LP: #1420027
    - CVE-2015-1465
  * x86, mm/ASLR: Fix stack randomization on 64-bit systems
    - LP: #1423757
    - CVE-2015-1593
  * net: llc: use correct size for sysctl timeout entries
    - LP: #1425271
    - CVE-2015-2041
  * net: rds: use correct size for max unacked packets and bytes
    - LP: #1425274
    - CVE-2015-2042
  * Btrfs: clear compress-force when remounting with compress option
    - LP: #1434183
  * ext4: merge uninitialized extents
    - LP: #1430184
  * btrfs: filter invalid arg for btrfs resize
    - LP: #1435441
  * Bluetooth: Add firmware update for Atheros 0cf3:311f
  * Bluetooth: btusb: Add IMC Networks (Broadcom based)
  * Bluetooth: sort the list of IDs in the source code
  * Bluetooth: append new supported device to the list [0b05:17d0]
  * Bluetooth: Add support for Intel bootloader devices
  * Bluetooth: Ignore isochronous endpoints for Intel USB bootloader
  * Bluetooth: Add support for Acer [13D3:3432]
  * Bluetooth: Add support for Broadcom device of Asus Z97-DELUXE
    motherboard
  * Add a new PID/VID 0227/0930 for AR3012.
  * Bluetooth: Add support for Acer [0489:e078]
  * Bluetooth: Add USB device 04ca:3010 as Atheros AR3012
  * x86: mm: move mmap_sem unlock from mm_fault_error() to caller
  * vm: add VM_FAULT_SIGSEGV handling support
  * vm: make stack guard page errors return VM_FAULT_SIGSEGV rather than
    SIGBUS
  * spi/pxa2xx: Clear cur_chip pointer before starting next message
  * spi: dw: Fix detecting FIFO depth
  * spi: dw-mid: fix FIFO size
  * ASoC: wm8960: Fix capture sample rate from 11250 to 11025
  * regulator: core: fix race condition in regulator_put()
  * ASoC: omap-mcbsp: Correct CBM_CFS dai format configuration
  * can: c_can: end pending transmission on network stop (ifdown)
  * nfs: fix dio deadlock when O_DIRECT flag is flipped
  * NFSv4.1: Fix an Oops in nfs41_...