tuntap: correctly set SOCKWQ_ASYNC_NOSPACE

[Nicolas Dichtel]

[SRU Justification]

== Impact ==

1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()") which is part of kernel v4.5 introduced an issue where userspace processes might not get notified if a link comes up after initially being down. This was fixed in the requested backport (from 4.17).

== Fix ==

Backport the requested patch to Bionic (4.15). Xenial (4.4) is not affected and Disco and later already contain that fix.

== Risk of Regregression ==

The change only slightly modifies a very specific protocol function. Risk should be low and limited to tuntap.

---

The upstream commit 2f3ab6221e4c ("tuntap: correctly set SOCKWQ_ASYNC_NOSPACE") is missing.
Without this patch, userspace apps that use tuntap may be blocked.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2f3ab6221e4c

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1830756

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1830756

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

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-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

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!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.15.0-65.74

---------------
linux (4.15.0-65.74) bionic; urgency=medium

  * bionic/linux: 4.15.0-65.74 -proposed tracker (LP: #1844403)

  * arm64: large modules fail to load (LP: #1841109)
    - arm64/kernel: kaslr: reduce module randomization range to 4 GB
    - arm64/kernel: don't ban ADRP to work around Cortex-A53 erratum #843419
    - arm64: fix undefined reference to 'printk'
    - arm64/kernel: rename module_emit_adrp_veneer->module_emit_veneer_for_adrp
    - [config] Remove CONFIG_ARM64_MODULE_CMODEL_LARGE

  * CVE-2018-20976
    - xfs: clear sb->s_fs_info on mount failure

  * br_netfilter: namespace sysctl operations (LP: #1836910)
    - net: bridge: add bitfield for options and convert vlan opts
    - net: bridge: convert nf call options to bits
    - netfilter: bridge: port sysctls to use brnf_net
    - netfilter: bridge: namespace bridge netfilter sysctls
    - netfilter: bridge: prevent UAF in brnf_exit_net()

  * tuntap: correctly set SOCKWQ_ASYNC_NOSPACE (LP: #1830756)
    - tuntap: correctly set SOCKWQ_ASYNC_NOSPACE

  * Bionic update: upstream stable patchset 2019-08-30 (LP: #1842114)
    - HID: Add 044f:b320 ThrustMaster, Inc. 2 in 1 DT
    - MIPS: kernel: only use i8253 clocksource with periodic clockevent
    - mips: fix cacheinfo
    - netfilter: ebtables: fix a memory leak bug in compat
    - ASoC: dapm: Fix handling of custom_stop_condition on DAPM graph walks
    - bonding: Force slave speed check after link state recovery for 802.3ad
    - can: dev: call netif_carrier_off() in register_candev()
    - ASoC: Fail card instantiation if DAI format setup fails
    - st21nfca_connectivity_event_received: null check the allocation
    - st_nci_hci_connectivity_event_received: null check the allocation
    - ASoC: ti: davinci-mcasp: Correct slot_width posed constraint
    - net: usb: qmi_wwan: Add the BroadMobi BM818 card
    - qed: RDMA - Fix the hw_ver returned in device attributes
    - isdn: mISDN: hfcsusb: Fix possible null-pointer dereferences in
      start_isoc_chain()
    - netfilter: ipset: Fix rename concurrency with listing
    - isdn: hfcsusb: Fix mISDN driver crash caused by transfer buffer on the stack
    - perf bench numa: Fix cpu0 binding
    - can: sja1000: force the string buffer NULL-terminated
    - can: peak_usb: force the string buffer NULL-terminated
    - net/ethernet/qlogic/qed: force the string buffer NULL-terminated
    - NFSv4: Fix a potential sleep while atomic in nfs4_do_reclaim()
    - HID: input: fix a4tech horizontal wheel custom usage
    - SMB3: Kernel oops mounting a encryptData share with CONFIG_DEBUG_VIRTUAL
    - net: cxgb3_main: Fix a resource leak in a error path in 'init_one()'
    - net: hisilicon: make hip04_tx_reclaim non-reentrant
    - net: hisilicon: fix hip04-xmit never return TX_BUSY
    - net: hisilicon: Fix dma_map_single failed on arm64
    - libata: have ata_scsi_rw_xlat() fail invalid passthrough requests
    - libata: add SG safety checks in SFF pio transfers
    - x86/lib/cpu: Address missing prototypes warning
    - drm/vmwgfx: fix memory leak when too many retries have occurred
    - perf ftrace: Fix failure to set cpuma...