scsi: core: Put LLD module refcnt after SCSI device is released

SCSI host release is triggered when SCSI device is freed. We have to make
sure that the low-level device driver module won't be unloaded before SCSI
host instance is released because shost->hostt is required in the release
handler.

Make sure to put LLD module refcnt after SCSI device is released.

Fixes a kernel panic of 'BUG: unable to handle page fault for address'
reported by Changhui and Yi.

Link: https://lore.kernel.org/r/20211008050118.1440686-1-ming.lei@redhat.com
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: Changhui Zhong <czhong@redhat.com>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index b241f9e..291ecc3 100644 (file)
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -553,8 +553,10 @@ EXPORT_SYMBOL(scsi_device_get);
  */
 void scsi_device_put(struct scsi_device *sdev)
 {
-       module_put(sdev->host->hostt->module);
+       struct module *mod = sdev->host->hostt->module;
+
        put_device(&sdev->sdev_gendev);
+       module_put(mod);
 }
 EXPORT_SYMBOL(scsi_device_put);
 

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 8679325..a35841b 100644 (file)
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -449,9 +449,12 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
        struct scsi_vpd *vpd_pg80 = NULL, *vpd_pg83 = NULL;
        struct scsi_vpd *vpd_pg0 = NULL, *vpd_pg89 = NULL;
        unsigned long flags;
+       struct module *mod;
 
        sdev = container_of(work, struct scsi_device, ew.work);
 
+       mod = sdev->host->hostt->module;
+
        scsi_dh_release_device(sdev);
 
        parent = sdev->sdev_gendev.parent;
@@ -502,11 +505,17 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 
        if (parent)
                put_device(parent);
+       module_put(mod);
 }
 
 static void scsi_device_dev_release(struct device *dev)
 {
        struct scsi_device *sdp = to_scsi_device(dev);
+
+       /* Set module pointer as NULL in case of module unloading */
+       if (!try_module_get(sdp->host->hostt->module))
+               sdp->host->hostt->module = NULL;
+
        execute_in_process_context(scsi_device_dev_release_usercontext,
                                   &sdp->ew);
 }