4.19-stable review patch. If anyone has any objections, please let me know.
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From: Guanghui Feng guanghuifeng@linux.alibaba.com
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@kernel.org Signed-off-by: Guanghui Feng guanghuifeng@linux.alibaba.com Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com Link: https://lore.kernel.org/r/1703152663-59949-1-git-send-email-guanghuifeng@lin... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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; }