From: Paul Durrant <pdurrant@amazon.com>
To: <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<xen-devel@lists.xenproject.org>
Cc: Paul Durrant <pdurrant@amazon.com>,
Jan Beulich <jbeulich@suse.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>
Subject: [PATCH v3 1/2] xen/xenbus: reference count registered modules
Date: Mon, 2 Dec 2019 11:41:16 +0000 [thread overview]
Message-ID: <20191202114117.1264-2-pdurrant@amazon.com> (raw)
In-Reply-To: <20191202114117.1264-1-pdurrant@amazon.com>
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(-)
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);
--
2.20.1
next prev parent reply other threads:[~2019-12-02 11:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-02 11:41 [PATCH v3 0/2] allow xen-blkback to be cleanly unloaded Paul Durrant
2019-12-02 11:41 ` Paul Durrant [this message]
2019-12-03 9:47 ` [PATCH v3 1/2] xen/xenbus: reference count registered modules Jan Beulich
2019-12-04 10:36 ` Jürgen Groß
2019-12-02 11:41 ` [PATCH v3 2/2] xen-blkback: allow module to be cleanly unloaded Paul Durrant
2019-12-04 10:36 ` Jürgen Groß
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