vduse_dev_open() looks up struct vduse_dev through the IDR and then
acquires dev->lock only after vduse_lock has been dropped.
This leaves a window where a concurrent VDUSE_DESTROY_DEV can remove the
same object from the IDR and free it before the open path locks the
device, leading to a use-after-free.
Close this race by keeping vduse_lock held until dev->lock has been
acquired in the open path, matching the lock ordering already used by
the destroy path.
Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Signed-off-by: Qihang Tang <[email protected]>
---
v2 -> v3:
- keep vduse_lock held until after dropping dev->lock
in vduse_dev_open()
- add changelog requested in review
v1 -> v2:
- add Fixes tag
- remove helper and inline the locking in
vduse_dev_open()
drivers/vdpa/vdpa_user/vduse_dev.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
b/drivers/vdpa/vdpa_user/vduse_dev.c
index 6202f6902fcd..d5c34260ed68 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1637,26 +1637,18 @@ static int vduse_dev_release(struct inode *inode,
struct file *file)
return 0;
}
-static struct vduse_dev *vduse_dev_get_from_minor(int minor)
+static int vduse_dev_open(struct inode *inode, struct file *file)
{
+ int ret = -EBUSY;
struct vduse_dev *dev;
mutex_lock(&vduse_lock);
- dev = idr_find(&vduse_idr, minor);
- mutex_unlock(&vduse_lock);
-
- return dev;
-}
-
-static int vduse_dev_open(struct inode *inode, struct file *file)
-{
- int ret;
- struct vduse_dev *dev = vduse_dev_get_from_minor(iminor(inode));
-
- if (!dev)
+ dev = idr_find(&vduse_idr, iminor(inode));
+ if (!dev) {
+ mutex_unlock(&vduse_lock);
return -ENODEV;
+ }
- ret = -EBUSY;
mutex_lock(&dev->lock);
if (dev->connected)
goto unlock;
@@ -1666,6 +1658,7 @@ static int vduse_dev_open(struct inode *inode, struct
file *file)
file->private_data = dev;
unlock:
mutex_unlock(&dev->lock);
+ mutex_unlock(&vduse_lock);
return ret;
}
--
2.39.5 (Apple Git-154)
