[PATCH] scsi: mpt3sas: fix kernel panic in scsih_qcmd after shutdown/unload

[Fengfei Xi]

We encountered a kernel crash problem after the user performed a 
shutdown operation. By analyzing the vmcore file, it is confirmed 
that it is scsih_qcmd called memset to access ioc->request resources 
that have been released in shutdown/module unload path.

crash> struct MPT3SAS_ADAPTER 0xffff00ff85806880
struct MPT3SAS_ADAPTER {
  list = {
    next = 0xffff800008eb8038 <mpt3sas_ioc_list>,
    prev = 0xffff800008eb8038 <mpt3sas_ioc_list>
  },
  ...
  name = "mpt3sas_cm0\000\000\000\000\000\000\000\
  ...
  remove_host = 1 '\001',
  ...
  request_sz = 128,
  request = 0x0,
  ...
  sense = 0x0,

The SCSI queuecommand handlers(scsih_qcmd) may be invoked after 
shutdown/unload, depending on other components. So we should add 
checks for 'ioc->remove_host' in scsih_qcmd, so not to access 
pointers/resources potentially freed in the PCI shutdown/module 
unload path.

Just like the following commit:
  9ff549ffb4fb4cc9a4b24d1de9dc3e68287797c4
  scsi: mpt3sas: fix oops in error handlers after shutdown/unload

Signed-off-by: Fengfei Xi <xi.fengfei@xxxxxxx>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index b519f4b59..d8994eaec 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -5140,7 +5140,8 @@ scsih_qcmd(struct Scsi_Host *shost, struct scsi_cmnd *scmd)
 		scsi_print_command(scmd);
 
 	sas_device_priv_data = scmd->device->hostdata;
-	if (!sas_device_priv_data || !sas_device_priv_data->sas_target) {
+	if (!sas_device_priv_data || !sas_device_priv_data->sas_target ||
+	    ioc->remove_host) {
 		scmd->result = DID_NO_CONNECT << 16;
 		scsi_done(scmd);
 		return 0;
-- 
2.17.1