CVE-2021-47290

In the Linux kernel, the following vulnerability has been resolved:

scsi: target: Fix NULL dereference on XCOPY completion

CPU affinity control added with commit 39ae3edda325 ("scsi: target: core:

Make completion affinity configurable") makes target_complete_cmd() queue

work on a CPU based on se_tpg->se_tpg_wwn->cmd_compl_affinity state.

LIO's EXTENDED COPY worker is a special case in that read/write cmds are

dispatched using the global xcopy_pt_tpg, which carries a NULL se_tpg_wwn

pointer following initialization in target_xcopy_setup_pt().

The NULL xcopy_pt_tpg->se_tpg_wwn pointer is dereferenced on completion of

any EXTENDED COPY initiated read/write cmds. E.g using the libiscsi

SCSI.ExtendedCopy.Simple test:

BUG: kernel NULL pointer dereference, address: 00000000000001a8

RIP: 0010:target_complete_cmd+0x9d/0x130 [target_core_mod]

Call Trace:

fd_execute_rw+0x148/0x42a [target_core_file]

? __dynamic_pr_debug+0xa7/0xe0

? target_check_reservation+0x5b/0x940 [target_core_mod]

__target_execute_cmd+0x1e/0x90 [target_core_mod]

transport_generic_new_cmd+0x17c/0x330 [target_core_mod]

target_xcopy_issue_pt_cmd+0x9/0x60 [target_core_mod]

target_xcopy_read_source.isra.7+0x10b/0x1b0 [target_core_mod]

? target_check_fua+0x40/0x40 [target_core_mod]

? transport_complete_task_attr+0x130/0x130 [target_core_mod]

target_xcopy_do_work+0x61f/0xc00 [target_core_mod]

This fix makes target_complete_cmd() queue work on se_cmd->cpuid if

se_tpg_wwn is NULL.