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scsi: ch: fixup refcounting imbalance for SCSI devices

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The SCSI device is required to be present during ch_probe() and ch_open().
But the SCSI device itself is only checked during ch_open(), so it's anyones
guess if it had been present during ch_probe(). And consequently we can't
reliably detach it during ch_release(), as ch_remove() might have been
called first.  So initialize the changer device during ch_probe(), and take
a reference to the SCSI device during both ch_probe() and ch_open().

[mkp: fixed checkpatch warning]

Link: https://lore.kernel.org/r/20200213153207.123357-2-hare@suse.de
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Hannes Reinecke 2020-02-13 16:32:05 +01:00 committed by Martin K. Petersen
parent 1939295a8d
commit 66167283c2
1 changed files with 18 additions and 4 deletions
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22
drivers/scsi/ch.c
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@ -569,6 +569,7 @@ static void ch_destroy(struct kref *ref)
{
scsi_changer *ch = container_of(ref, scsi_changer, ref);
ch->device = NULL;
kfree(ch->dt);
kfree(ch);
}
@ -594,14 +595,17 @@ ch_open(struct inode *inode, struct file *file)
spin_lock(&ch_index_lock);
ch = idr_find(&ch_index_idr, minor);
if (NULL == ch || scsi_device_get(ch->device)) {
if (ch == NULL || !kref_get_unless_zero(&ch->ref)) {
spin_unlock(&ch_index_lock);
mutex_unlock(&ch_mutex);
return -ENXIO;
}
kref_get(&ch->ref);
spin_unlock(&ch_index_lock);
if (scsi_device_get(ch->device)) {
kref_put(&ch->ref, ch_destroy);
mutex_unlock(&ch_mutex);
return -ENXIO;
}
file->private_data = ch;
mutex_unlock(&ch_mutex);
return 0;
@ -938,6 +942,12 @@ static int ch_probe(struct device *dev)
ch->minor = ret;
sprintf(ch->name,"ch%d",ch->minor);
ret = scsi_device_get(sd);
if (ret) {
sdev_printk(KERN_WARNING, sd, "ch%d: failed to get device\n",
ch->minor);
goto remove_idr;
}
class_dev = device_create(ch_sysfs_class, dev,
MKDEV(SCSI_CHANGER_MAJOR, ch->minor), ch,
@ -946,7 +956,7 @@ static int ch_probe(struct device *dev)
sdev_printk(KERN_WARNING, sd, "ch%d: device_create failed\n",
ch->minor);
ret = PTR_ERR(class_dev);
goto remove_idr;
goto put_device;
}
mutex_init(&ch->lock);
@ -964,6 +974,8 @@ static int ch_probe(struct device *dev)
return 0;
destroy_dev:
device_destroy(ch_sysfs_class, MKDEV(SCSI_CHANGER_MAJOR, ch->minor));
put_device:
scsi_device_put(sd);
remove_idr:
idr_remove(&ch_index_idr, ch->minor);
free_ch:
@ -977,9 +989,11 @@ static int ch_remove(struct device *dev)
spin_lock(&ch_index_lock);
idr_remove(&ch_index_idr, ch->minor);
dev_set_drvdata(dev, NULL);
spin_unlock(&ch_index_lock);
device_destroy(ch_sysfs_class, MKDEV(SCSI_CHANGER_MAJOR,ch->minor));
scsi_device_put(ch->device);
kref_put(&ch->ref, ch_destroy);
return 0;
}