4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Guanghui Feng <guanghuifeng@xxxxxxxxxxxxxxxxx>
commit 0c9ae0b8605078eafc3bea053cc78791e97ba2e2 upstream.
core-1 core-2
-------------------------------------------------------
uio_unregister_device uio_open
idev = idr_find()
device_unregister(&idev->dev)
put_device(&idev->dev)
uio_device_release
get_device(&idev->dev)
kfree(idev)
uio_free_minor(minor)
uio_release
put_device(&idev->dev)
kfree(idev)
-------------------------------------------------------
In the core-1 uio_unregister_device(), the device_unregister will kfree
idev when the idev->dev kobject ref is 1. But after core-1
device_unregister, put_device and before doing kfree, the core-2 may
get_device. Then:
1. After core-1 kfree idev, the core-2 will do use-after-free for idev.
2. When core-2 do uio_release and put_device, the idev will be double
freed.
To address this issue, we can get idev atomic & inc idev reference with
minor_lock.
Fixes: 57c5f4df0a5a ("uio: fix crash after the device is unregistered")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Guanghui Feng <guanghuifeng@xxxxxxxxxxxxxxxxx>
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1703152663-59949-1-git-send-email-guanghuifeng@xxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/uio/uio.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -464,13 +464,13 @@ static int uio_open(struct inode *inode,
mutex_lock(&minor_lock);
idev = idr_find(&uio_idr, iminor(inode));
- mutex_unlock(&minor_lock);
if (!idev) {
ret = -ENODEV;
+ mutex_unlock(&minor_lock);
goto out;
}
-
get_device(&idev->dev);
+ mutex_unlock(&minor_lock);
if (!try_module_get(idev->owner)) {
ret = -ENODEV;
@@ -1019,9 +1019,8 @@ void uio_unregister_device(struct uio_in
idev->info = NULL;
mutex_unlock(&idev->info_lock);
- device_unregister(&idev->dev);
-
uio_free_minor(minor);
+ device_unregister(&idev->dev);
return;
}
