5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Juergen Gross <jgross@xxxxxxxx>
[ Upstream commit 2f69a110e7bba3ec6bc089a2f736ca0941d887ed ]
Commit 060eabe8fbe726 ("xenbus/backend: Protect xenbus callback with
lock") introduced a bug by holding a lock while calling a function
which might schedule.
Fix that by using a semaphore instead.
Fixes: 060eabe8fbe726 ("xenbus/backend: Protect xenbus callback with lock")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Link: https://lore.kernel.org/r/20200305100323.16736-1-jgross@xxxxxxxx
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Stable-dep-of: afc545da381b ("xen: Fix the issue of resource not being properly released in xenbus_dev_probe()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/xen/xenbus/xenbus_probe.c | 10 +++++-----
drivers/xen/xenbus/xenbus_probe_backend.c | 5 +++--
include/xen/xenbus.h | 3 ++-
3 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 1ad5bc9dd6cc4..b88512d92ef52 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -240,9 +240,9 @@ int xenbus_dev_probe(struct device *_dev)
goto fail;
}
- spin_lock(&dev->reclaim_lock);
+ down(&dev->reclaim_sem);
err = drv->probe(dev, id);
- spin_unlock(&dev->reclaim_lock);
+ up(&dev->reclaim_sem);
if (err)
goto fail_put;
@@ -273,9 +273,9 @@ int xenbus_dev_remove(struct device *_dev)
free_otherend_watch(dev);
if (drv->remove) {
- spin_lock(&dev->reclaim_lock);
+ down(&dev->reclaim_sem);
drv->remove(dev);
- spin_unlock(&dev->reclaim_lock);
+ up(&dev->reclaim_sem);
}
module_put(drv->driver.owner);
@@ -489,7 +489,7 @@ int xenbus_probe_node(struct xen_bus_type *bus,
goto fail;
dev_set_name(&xendev->dev, "%s", devname);
- spin_lock_init(&xendev->reclaim_lock);
+ sema_init(&xendev->reclaim_sem, 1);
/* Register with generic device framework. */
err = device_register(&xendev->dev);
diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
index 54aefbbbbff9e..8c76b94f0512d 100644
--- a/drivers/xen/xenbus/xenbus_probe_backend.c
+++ b/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -45,6 +45,7 @@
#include <linux/mm.h>
#include <linux/notifier.h>
#include <linux/export.h>
+#include <linux/semaphore.h>
#include <asm/page.h>
#include <asm/pgtable.h>
@@ -265,10 +266,10 @@ static int backend_reclaim_memory(struct device *dev, void *data)
drv = to_xenbus_driver(dev->driver);
if (drv && drv->reclaim_memory) {
xdev = to_xenbus_device(dev);
- if (!spin_trylock(&xdev->reclaim_lock))
+ if (down_trylock(&xdev->reclaim_sem))
return 0;
drv->reclaim_memory(xdev);
- spin_unlock(&xdev->reclaim_lock);
+ up(&xdev->reclaim_sem);
}
return 0;
}
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 0d166dfe48334..372c7c69cdf6e 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -42,6 +42,7 @@
#include <linux/completion.h>
#include <linux/init.h>
#include <linux/slab.h>
+#include <linux/semaphore.h>
#include <xen/interface/xen.h>
#include <xen/interface/grant_table.h>
#include <xen/interface/io/xenbus.h>
@@ -85,7 +86,7 @@ struct xenbus_device {
enum xenbus_state state;
struct completion down;
struct work_struct work;
- spinlock_t reclaim_lock;
+ struct semaphore reclaim_sem;
};
static inline struct xenbus_device *to_xenbus_device(struct device *dev)
--
2.43.0
