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xen/xenbus: reference count registered modules 

To prevent a PV driver module being removed whilst attached to its other
end, and hence xenbus calling into potentially invalid text, take a
reference on the module before calling the probe() method (dropping it if
unsuccessful) and drop the reference after returning from the remove()
method.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Paul Durrant 2019-12-02 11:41:16 +00:00 committed by Juergen Gross
parent b3f7931f5c
commit 196748a276
1 changed files with 12 additions and 1 deletions
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13
drivers/xen/xenbus/xenbus_probe.c
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@ -232,9 +232,16 @@ int xenbus_dev_probe(struct device *_dev)
return err;
}
if (!try_module_get(drv->driver.owner)) {
dev_warn(&dev->dev, "failed to acquire module reference on '%s'\n",
drv->driver.name);
err = -ESRCH;
goto fail;
}
err = drv->probe(dev, id);
if (err)
goto fail;
goto fail_put;
err = watch_otherend(dev);
if (err) {
@ -244,6 +251,8 @@ int xenbus_dev_probe(struct device *_dev)
}
return 0;
fail_put:
module_put(drv->driver.owner);
fail:
xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
xenbus_switch_state(dev, XenbusStateClosed);
@ -263,6 +272,8 @@ int xenbus_dev_remove(struct device *_dev)
if (drv->remove)
drv->remove(dev);
module_put(drv->driver.owner);
free_otherend_details(dev);
xenbus_switch_state(dev, XenbusStateClosed);