CVE-2021-47178CVE-2021-47178

In the Linux kernel, the following vulnerability has been resolved: scsi: target: core: Avoid smp_processor_id() in preemptible code The BUG message "BUG: using smp_processor_id() in preemptible [00000000] code" was observed for TCMU devices with kernel config DEBUG_PREEMPT. The message was observed when blktests block/005 was run on TCMU devices with fileio backend or user:zbc backend [1]. The commit 1130b499b4a7 ("scsi: target: tcm_loop: Use LIO wq cmd submission helper") triggered the symptom. The commit modified work queue to handle commands and changed 'current->nr_cpu_allowed' at smp_processor_id() call. The message was also observed at system shutdown when TCMU devices were not cleaned up [2]. The function smp_processor_id() was called in SCSI host work queue for abort handling, and triggered the BUG message. This symptom was observed regardless of the commit 1130b499b4a7 ("scsi: target: tcm_loop: Use LIO wq cmd submission helper"). To avoid the preemptible code check at sm