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scsi: ch: synchronize ch_probe() and ch_open()

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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.

Link: https://lore.kernel.org/r/20200213153207.123357-3-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 16:32:06 +01:00 committed by Martin K. Petersen
parent 66167283c2
commit 1c7ce4bcfb
1 changed files with 11 additions and 4 deletions
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15
drivers/scsi/ch.c
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@ -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);