[v3,1/2] xen/xenbus: reference count registered modules
diff mbox series

Message ID 20191202114117.1264-2-pdurrant@amazon.com
State New, archived
Headers show
Series
  • allow xen-blkback to be cleanly unloaded
Related show

Commit Message

Paul Durrant Dec. 2, 2019, 11:41 a.m. UTC
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>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>

v2:
 - New in v2

v3:
 - Use try_module_get() rather than __module)get() and handle failure
 - Not added Juergen's R-b because of the change
---
 drivers/xen/xenbus/xenbus_probe.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Comments

Jan Beulich Dec. 3, 2019, 9:47 a.m. UTC | #1
On 02.12.2019 12:41, Paul Durrant wrote:
> 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>
with ...

> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -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);

... perhaps the full stop dropped here and ...

> +		err = -ESRCH;
> +		goto fail;
> +        }

... (definitely) indentation here changed to use a tab.

Jan
Jürgen Groß Dec. 4, 2019, 10:36 a.m. UTC | #2
On 02.12.19 12:41, Paul Durrant wrote:
> 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>

Pushed to xen/tip.git for-linus-5.5b


Juergen

Patch
diff mbox series

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5b471889d723..4461f4583476 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -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);