The TCM_LOOP LUN creation process calls device_register() to create the
device, which in turn invokes tcm_loop_driver_probe() registered with
the TCM_LOOP bus to create and register the scsi_host.  However, if the
scsi_host memory allocation fails or scsi_add_host() fails, the
device_register() process still returns success.  Subsequently, when the
user binds the LUN to a specific backend device, it accesses the NULL or
freed scsi_host.

Crash Call Trace:
  RIP: 0010:scsi_is_host_device+0x7/0x20
  scsi_alloc_target+0x32/0x2c0
  __scsi_add_device+0x41/0xf0
  scsi_add_device+0xd/0x30
  tcm_loop_port_link+0x25/0x50 [tcm_loop]
  target_fabric_port_link+0x9c/0xb0 [target_core_mod]
  ...

This issue is fixed by:

 1. Setting the tcm_loop_hba's scsi_host to NULL, if scsi_add_host()
    fails.

 2. Checking the tcm_loop_hba's scsi_host after device_register().

 3. Checking the tcm_loop_hba's scsi_host in tcm_loop_driver_remove().

Fixes: 3703b2c5d041 ("[SCSI] tcm_loop: Add multi-fabric Linux/SCSI LLD fabric module")
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260424013923.25998-1-kanie@linux.alibaba.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Pull in fixes to resolve mpi3mr merge conflict.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

tcm_loop_target_reset() violates the SCSI EH contract: it returns SUCCESS
without draining any in-flight commands.  The SCSI EH documentation
(scsi_eh.rst) requires that when a reset handler returns SUCCESS the driver
has made lower layers "forget about timed out scmds" and is ready for new
commands.  Every other SCSI LLD (virtio_scsi, mpt3sas, ipr, scsi_debug,
mpi3mr) enforces this by draining or completing outstanding commands before
returning SUCCESS.

Because tcm_loop_target_reset() doesn't drain, the SCSI EH reuses in-flight
scsi_cmnd structures for recovery commands (e.g. TUR) while the target core
still has async completion work queued for the old se_cmd.  The memset in
queuecommand zeroes se_lun and lun_ref_active, causing
transport_lun_remove_cmd() to skip its percpu_ref_put().  The leaked LUN
reference prevents transport_clear_lun_ref() from completing, hanging
configfs LUN unlink forever in D-state:

  INFO: task rm:264 blocked for more than 122 seconds.
  rm              D    0   264    258 0x00004000
  Call Trace:
   __schedule+0x3d0/0x8e0
   schedule+0x36/0xf0
   transport_clear_lun_ref+0x78/0x90 [target_core_mod]
   core_tpg_remove_lun+0x28/0xb0 [target_core_mod]
   target_fabric_port_unlink+0x50/0x60 [target_core_mod]
   configfs_unlink+0x156/0x1f0 [configfs]
   vfs_unlink+0x109/0x290
   do_unlinkat+0x1d5/0x2d0

Fix this by making tcm_loop_target_reset() actually drain commands:

 1. Issue TMR_LUN_RESET via tcm_loop_issue_tmr() to drain all commands that
    the target core knows about (those not yet CMD_T_COMPLETE).

 2. Use blk_mq_tagset_busy_iter() to iterate all started requests and
    flush_work() on each se_cmd — this drains any deferred completion work
    for commands that already had CMD_T_COMPLETE set before the TMR (which
    the TMR skips via __target_check_io_state()).  This is the same pattern
    used by mpi3mr, scsi_debug, and libsas to drain outstanding commands
    during reset.

Fixes: e0eb5d38b732 ("scsi: target: tcm_loop: Use block cmd allocator for se_cmds")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://patch.msgid.link/27011aa34c8f6b1b94d2e3cf5655b6d037f53428.1773706803.git.josef@toxicpanda.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

This has us use the driver's completion preference by default. There is
no behavior changes with this patch and we queue completion to LIO's
completion workqueue by default.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260222232946.7637-3-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

This was done entirely with mindless brute force, using

    git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
        xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook <kees@kernel.org>

In clang version 21.1 and later the -Wimplicit-enum-enum-cast warning
option has been introduced. This warning is enabled by default and can
be used to catch .queuecommand() implementations that return another
value than 0 or one of the SCSI_MLQUEUE_* constants. Hence this patch
that changes the return type of the .queuecommand() implementations from
'int' into 'enum scsi_qc_status'. No functionality has been changed.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/20260115210357.2501991-6-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

If the allocation of tl_hba->sh fails in tcm_loop_driver_probe() and we
attempt to dereference it in tcm_loop_tpg_address_show() we will get a
segfault, see below for an example. So, check tl_hba->sh before
dereferencing it.

  Unable to allocate struct scsi_host
  BUG: kernel NULL pointer dereference, address: 0000000000000194
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 1 PID: 8356 Comm: tokio-runtime-w Not tainted 6.6.104.2-4.azl3 #1
  Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 09/28/2024
  RIP: 0010:tcm_loop_tpg_address_show+0x2e/0x50 [tcm_loop]
...
  Call Trace:
   <TASK>
   configfs_read_iter+0x12d/0x1d0 [configfs]
   vfs_read+0x1b5/0x300
   ksys_read+0x6f/0xf0
...

Cc: stable@vger.kernel.org
Fixes: 2628b352c3d4 ("tcm_loop: Show address of tpg in configfs")
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Allen Pais <apais@linux.microsoft.com>
Link: https://patch.msgid.link/1762370746-6304-1-git-send-email-hamzamahfooz@linux.microsoft.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

When the tcm_loop_nr_hw_queues is set to a value greater than 1, the
tags of requests in the block layer are no longer unique. This may lead
to erroneous aborting of commands with the same tag. The issue can be
resolved by using blk_mq_unique_tag to generate globally unique
identifiers by combining the hardware queue index and per-queue tags.

Fixes: 6375f8908255 ("tcm_loop: Fixup tag handling")
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250313014728.105849-1-kanie@linux.alibaba.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Now that the driver core can properly handle constant struct bus_type, move
the tcm_loop_lld_bus variable to be a constant structure as well, placing
it into read-only memory which can not be modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240204-bus_cleanup-target-v1-1-96106936c4ab@marliere.net
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>