cifs: On cifs_reconnect, resolve the hostname again

[Tim Gardner]

SRU Justification

[Impact]

The Microsoft CIFS team is requesting below patch to be backported for 5.4 Azure tuned kernel

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4e456b30f78c429b183db420e23b26cde7e03a78

A customer is encountering the bug fixed by this patch.

[Fix]

7d397a034d5c45528c7bdf7fc3752c4793029cce cifs: rename reconn_inval_dfs_target()
7d6535b720421d58886d5590ffc3617d359aa871 cifs: Simplify reconnect code when dfs upcall is enabled
4e456b30f78c429b183db420e23b26cde7e03a78 cifs: On cifs_reconnect, resolve the hostname again.

The first 2 patches are scaffolding to make the backport simpler. the 3rd patch is the bug fix.

[Test Plan]

The test kernel at https://launchpad.net/~timg-tpi/+archive/ubuntu/cifs-reconnect-sf00309672 has been found to fix the issue.

[Where problems could occur]

This could perturb CIFS connections in new and different ways.

[Other Info]

https://canonical.my.salesforce.com/5004K000005pQNG

[Tim Gardner (timg-tpi)]

Patches submitted: https://lists.ubuntu.com/archives/kernel-team/2021-May/120821.html

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-azure - 5.4.0-1049.51

---------------
linux-azure (5.4.0-1049.51) focal; urgency=medium

  * focal/linux-azure: 5.4.0-1049.51 -proposed tracker (LP: #1930703)

  * cifs: On cifs_reconnect, resolve the hostname again (LP: #1929831)
    - cifs: rename reconn_inval_dfs_target()
    - cifs: Simplify reconnect code when dfs upcall is enabled
    - cifs: Avoid error pointer dereference
    - cifs: On cifs_reconnect, resolve the hostname again.

 -- Tim Gardner <email address hidden> Thu, 03 Jun 2021 09:17:13 -0600

[Marcelo Cerri (mhcerri)]

Latest version of the patch set with additional fixes from upstream:

https://lists.ubuntu.com/archives/kernel-team/2021-June/121485.html

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

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!

[Tim Gardner (timg-tpi)]

I am tagging this verification done. MSFT has been using this patch set in the Azure derivative kernel for several weeks and have confirmed it fixes the issue.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 5.4.0-81.91

---------------
linux (5.4.0-81.91) focal; urgency=medium

  * Packaging resync (LP: #1786013)
    - update dkms package versions

  * large_dir in ext4 broken (LP: #1933074)
    - SAUCE: ext4: fix directory index node split corruption

  * Some test in kselftest/net on focal source tree were not tested at all
    (LP: #1934282)
    - selftests/net: add missing tests to Makefile

  * curtin: install flash-kernel in arm64 UEFI unexpected (LP: #1918427)
    - [Packaging] Allow grub-efi-arm* to satisfy recommends on ARM

  * Add l2tp.sh in net from ubuntu_kernel_selftests back (LP: #1934293)
    - Revert "UBUNTU: SAUCE: selftests/net -- disable l2tp.sh test"

  * icmp_redirect.sh in net from ubuntu_kernel_selftests failed on F-OEM-5.6 /
    F-OEM-5.10 / F-OEM-5.13 / F / G / H (LP: #1880645)
    - selftests: icmp_redirect: support expected failures

  * Focal update: v5.4.128 upstream stable release (LP: #1934179)
    - dmaengine: ALTERA_MSGDMA depends on HAS_IOMEM
    - dmaengine: QCOM_HIDMA_MGMT depends on HAS_IOMEM
    - dmaengine: stedma40: add missing iounmap() on error in d40_probe()
    - afs: Fix an IS_ERR() vs NULL check
    - mm/memory-failure: make sure wait for page writeback in memory_failure
    - kvm: LAPIC: Restore guard to prevent illegal APIC register access
    - batman-adv: Avoid WARN_ON timing related checks
    - net: ipv4: fix memory leak in netlbl_cipsov4_add_std
    - vrf: fix maximum MTU
    - net: rds: fix memory leak in rds_recvmsg
    - net: lantiq: disable interrupt before sheduling NAPI
    - udp: fix race between close() and udp_abort()
    - rtnetlink: Fix regression in bridge VLAN configuration
    - net/sched: act_ct: handle DNAT tuple collision
    - net/mlx5e: Remove dependency in IPsec initialization flows
    - net/mlx5e: Fix page reclaim for dead peer hairpin
    - net/mlx5: Consider RoCE cap before init RDMA resources
    - net/mlx5e: allow TSO on VXLAN over VLAN topologies
    - net/mlx5e: Block offload of outer header csum for UDP tunnels
    - netfilter: synproxy: Fix out of bounds when parsing TCP options
    - sch_cake: Fix out of bounds when parsing TCP options and header
    - alx: Fix an error handling path in 'alx_probe()'
    - net: stmmac: dwmac1000: Fix extended MAC address registers definition
    - net: make get_net_ns return error if NET_NS is disabled
    - qlcnic: Fix an error handling path in 'qlcnic_probe()'
    - netxen_nic: Fix an error handling path in 'netxen_nic_probe()'
    - net: qrtr: fix OOB Read in qrtr_endpoint_post
    - ptp: improve max_adj check against unreasonable values
    - net: cdc_ncm: switch to eth%d interface naming
    - lantiq: net: fix duplicated skb in rx descriptor ring
    - net: usb: fix possible use-after-free in smsc75xx_bind
    - net: fec_ptp: fix issue caused by refactor the fec_devtype
    - net: ipv4: fix memory leak in ip_mc_add1_src
    - net/af_unix: fix a data-race in unix_dgram_sendmsg / unix_release_sock
    - be2net: Fix an error handling path in 'be_probe()'
    - net: hamradio: fix memory leak in mkiss_close
    - net: cdc_eem: fix tx fixup skb leak
    - cxgb4: fix wrong shift.
    - bnx...