CVE-2021-47192

In the Linux kernel, the following vulnerability has been resolved: scsi:
core: sysfs: Fix hang when device state is set via sysfs This fixes a
regression added with: commit f0f82e2476f6 (“scsi: core: Fix capacity set
to zero after offlinining device”) The problem is that after iSCSI
recovery, iscsid will call into the kernel to set the dev’s state to
running, and with that patch we now call scsi_rescan_device() with the
state_mutex held. If the SCSI error handler thread is just starting to test
the device in scsi_send_eh_cmnd() then it’s going to try to grab the
state_mutex. We are then stuck, because when scsi_rescan_device() tries to
send its I/O scsi_queue_rq() calls -> scsi_host_queue_ready() ->
scsi_host_in_recovery() which will return true (the host state is still in
recovery) and I/O will just be requeued. scsi_send_eh_cmnd() will then
never be able to grab the state_mutex to finish error handling. To prevent
the deadlock move the rescan-related code to after we drop the state_mutex.
This also adds a check for if we are already in the running state. This
prevents extra scans and helps the iscsid case where if the transport class
has already onlined the device during its recovery process then we don’t
need userspace to do it again plus possibly block that daemon.