2022-08-29 18:33:56

by Russ Weight

Subject: [PATCH v2 1/1] firmware_loader: Fix use-after-free during unregister

In the following code within firmware_upload_unregister(), the call to
device_unregister() could result in the dev_release function freeing the
fw_upload_priv structure before it is dereferenced for the call to
module_put(). This bug was found by the kernel test robot using
CONFIG_KASAN while running the firmware selftests.

device_unregister(&fw_sysfs->dev);
module_put(fw_upload_priv->module);

The problem is fixed by copying fw_upload_priv->module to a local variable
for use when calling device_unregister().

Reported-by: kernel test robot <[email protected]>
Fixes: 97730bbb242c ("firmware_loader: Add firmware-upload support")
Signed-off-by: Russ Weight <[email protected]>
---
v2: Rebased to latest linux-next branch (next-20220829)
---
drivers/base/firmware_loader/sysfs_upload.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/firmware_loader/sysfs_upload.c b/drivers/base/firmware_loader/sysfs_upload.c
index 87044d52322a..63e15bddd80c 100644
--- a/drivers/base/firmware_loader/sysfs_upload.c
+++ b/drivers/base/firmware_loader/sysfs_upload.c
@@ -377,6 +377,7 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
{
struct fw_sysfs *fw_sysfs = fw_upload->priv;
struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
+ struct module *module = fw_upload_priv->module;

mutex_lock(&fw_upload_priv->lock);
if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
@@ -392,6 +393,6 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)

unregister:
device_unregister(&fw_sysfs->dev);
- module_put(fw_upload_priv->module);
+ module_put(module);
}
EXPORT_SYMBOL_GPL(firmware_upload_unregister);
--
2.25.1

2022-08-29 22:10:56

by Matthew Gerlach

Subject: Re: [PATCH v2 1/1] firmware_loader: Fix use-after-free during unregister

On Mon, 29 Aug 2022, Russ Weight wrote:

> In the following code within firmware_upload_unregister(), the call to
> device_unregister() could result in the dev_release function freeing the
> fw_upload_priv structure before it is dereferenced for the call to
> module_put(). This bug was found by the kernel test robot using
> CONFIG_KASAN while running the firmware selftests.
>
> device_unregister(&fw_sysfs->dev);
> module_put(fw_upload_priv->module);
>
> The problem is fixed by copying fw_upload_priv->module to a local variable
> for use when calling device_unregister().
>
> Reported-by: kernel test robot <[email protected]>
> Fixes: 97730bbb242c ("firmware_loader: Add firmware-upload support")
> Signed-off-by: Russ Weight <[email protected]>

Looks good to me.

Reviewed-by: Matthew Gerlach <[email protected]>
> ---
> v2: Rebased to latest linux-next branch (next-20220829)
> ---
> drivers/base/firmware_loader/sysfs_upload.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_loader/sysfs_upload.c b/drivers/base/firmware_loader/sysfs_upload.c
> index 87044d52322a..63e15bddd80c 100644
> --- a/drivers/base/firmware_loader/sysfs_upload.c
> +++ b/drivers/base/firmware_loader/sysfs_upload.c
> @@ -377,6 +377,7 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
> {
> struct fw_sysfs *fw_sysfs = fw_upload->priv;
> struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
> + struct module *module = fw_upload_priv->module;
>
> mutex_lock(&fw_upload_priv->lock);
> if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
> @@ -392,6 +393,6 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
>
> unregister:
> device_unregister(&fw_sysfs->dev);
> - module_put(fw_upload_priv->module);
> + module_put(module);
> }
> EXPORT_SYMBOL_GPL(firmware_upload_unregister);
> --
> 2.25.1
>
>