The 'ch' device node is created before the configuration is
being read in, which leads to a race window when ch_open() is called
before that.
To avoid any races we should be taking the device mutex during
ch_readconfig() and ch_init_elem(), and also during ch_open().
That ensures ch_probe is finished before ch_open() completes.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
drivers/scsi/ch.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/ch.c b/drivers/scsi/ch.c
index 974afb4bd5fe..9cbfb00ab950 100644
--- a/drivers/scsi/ch.c
+++ b/drivers/scsi/ch.c
@@ -606,7 +606,10 @@ ch_open(struct inode *inode, struct file *file)
mutex_unlock(&ch_mutex);
return -ENXIO;
}
+ /* Synchronize with ch_probe() */
+ mutex_lock(&ch->lock);
file->private_data = ch;
+ mutex_unlock(&ch->lock);
mutex_unlock(&ch_mutex);
return 0;
}
@@ -949,6 +952,9 @@ static int ch_probe(struct device *dev)
goto remove_idr;
}
+ mutex_init(&ch->lock);
+ kref_init(&ch->ref);
+ ch->device = sd;
class_dev = device_create(ch_sysfs_class, dev,
MKDEV(SCSI_CHANGER_MAJOR, ch->minor), ch,
"s%s", ch->name);
@@ -959,15 +965,16 @@ static int ch_probe(struct device *dev)
goto put_device;
}
- mutex_init(&ch->lock);
- kref_init(&ch->ref);
- ch->device = sd;
+ mutex_lock(&ch->lock);
ret = ch_readconfig(ch);
- if (ret)
+ if (ret) {
+ mutex_unlock(&ch->lock);
goto destroy_dev;
+ }
if (init)
ch_init_elem(ch);
+ mutex_unlock(&ch->lock);
dev_set_drvdata(dev, ch);
sdev_printk(KERN_INFO, sd, "Attached scsi changer %s\n", ch->name);
--
2.16.4
