2024-01-10 09:15:18

by Udipto Goswami

Subject: [PATCH v4] usb: core: Prevent null pointer dereference in update_port_device_state

Currently,the function update_port_device_state gets the usb_hub from
udev->parent by calling usb_hub_to_struct_hub.
However, in case the actconfig or the maxchild is 0, the usb_hub would
be NULL and upon further accessing to get port_dev would result in null
pointer dereference.

Fix this by introducing an if check after the usb_hub is populated.

Fixes: 83cb2604f641 ("usb: core: add sysfs entry for usb device state")
Cc: [email protected]
Signed-off-by: Udipto Goswami <[email protected]>
---
v4: Fixed minor mistakes in the comment.
v3: Re-wrote the comment for better context.
v2: Introduced comment for the if check & CC'ed stable.

drivers/usb/core/hub.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index ffd7c99e24a3..5ba1875e6bf4 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2053,9 +2053,22 @@ static void update_port_device_state(struct usb_device *udev)

if (udev->parent) {
hub = usb_hub_to_struct_hub(udev->parent);
- port_dev = hub->ports[udev->portnum - 1];
- WRITE_ONCE(port_dev->state, udev->state);
- sysfs_notify_dirent(port_dev->state_kn);
+
+ /*
+ * The Link Layer Validation System Driver (lvstest)
+ * has step to unbind the hub before running the rest
+ * of the procedure. This triggers hub_disconnect which
+ * will set the hub's maxchild to 0, further resulting
+ * usb_hub_to_struct_hub returning NULL.
+ *
+ * Add if check to avoid running into NULL pointer
+ * de-reference.
+ */
+ if (hub) {
+ port_dev = hub->ports[udev->portnum - 1];
+ WRITE_ONCE(port_dev->state, udev->state);
+ sysfs_notify_dirent(port_dev->state_kn);
+ }
}
}

--
2.17.1

2024-01-10 09:24:19

by Sergei Shtylyov

Subject: Re: [PATCH v4] usb: core: Prevent null pointer dereference in update_port_device_state

On 1/10/24 12:14 PM, Udipto Goswami wrote:

> Currently,the function update_port_device_state gets the usb_hub from

Need space between comma and "the"...

> udev->parent by calling usb_hub_to_struct_hub.
> However, in case the actconfig or the maxchild is 0, the usb_hub would
> be NULL and upon further accessing to get port_dev would result in null
> pointer dereference.
>
> Fix this by introducing an if check after the usb_hub is populated.
>
> Fixes: 83cb2604f641 ("usb: core: add sysfs entry for usb device state")
> Cc: [email protected]
> Signed-off-by: Udipto Goswami <[email protected]>
[...]

> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index ffd7c99e24a3..5ba1875e6bf4 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2053,9 +2053,22 @@ static void update_port_device_state(struct usb_device *udev)
>
> if (udev->parent) {
> hub = usb_hub_to_struct_hub(udev->parent);
> - port_dev = hub->ports[udev->portnum - 1];
> - WRITE_ONCE(port_dev->state, udev->state);
> - sysfs_notify_dirent(port_dev->state_kn);
> +
> + /*
> + * The Link Layer Validation System Driver (lvstest)
> + * has step to unbind the hub before running the rest
> + * of the procedure. This triggers hub_disconnect which
> + * will set the hub's maxchild to 0, further resulting

Resulting in.

> + * usb_hub_to_struct_hub returning NULL.
> + *
> + * Add if check to avoid running into NULL pointer
> + * de-reference.

This is obvious from the code below, I think...

> + */
> + if (hub) {
> + port_dev = hub->ports[udev->portnum - 1];
> + WRITE_ONCE(port_dev->state, udev->state);
> + sysfs_notify_dirent(port_dev->state_kn);
> + }
> }
> }
>

MBR, Sergey

2024-01-10 09:58:21

by Udipto Goswami

Subject: Re: [PATCH v4] usb: core: Prevent null pointer dereference in update_port_device_state

On 1/10/2024 2:52 PM, Sergei Shtylyov wrote:
> On 1/10/24 12:14 PM, Udipto Goswami wrote:
>
>> Currently,the function update_port_device_state gets the usb_hub from
>
> Need space between comma and "the"...
got it.
>
>> udev->parent by calling usb_hub_to_struct_hub.
>> However, in case the actconfig or the maxchild is 0, the usb_hub would
>> be NULL and upon further accessing to get port_dev would result in null
>> pointer dereference.
>>
>> Fix this by introducing an if check after the usb_hub is populated.
>>
>> Fixes: 83cb2604f641 ("usb: core: add sysfs entry for usb device state")
>> Cc: [email protected]
>> Signed-off-by: Udipto Goswami <[email protected]>
> [...]
>
>> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
>> index ffd7c99e24a3..5ba1875e6bf4 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -2053,9 +2053,22 @@ static void update_port_device_state(struct usb_device *udev)
>>
>> if (udev->parent) {
>> hub = usb_hub_to_struct_hub(udev->parent);
>> - port_dev = hub->ports[udev->portnum - 1];
>> - WRITE_ONCE(port_dev->state, udev->state);
>> - sysfs_notify_dirent(port_dev->state_kn);
>> +
>> + /*
>> + * The Link Layer Validation System Driver (lvstest)
>> + * has step to unbind the hub before running the rest
>> + * of the procedure. This triggers hub_disconnect which
>> + * will set the hub's maxchild to 0, further resulting
>
> Resulting in.

got it.
>
>> + * usb_hub_to_struct_hub returning NULL.
>> + *
>> + * Add if check to avoid running into NULL pointer
>> + * de-reference.
>
> This is obvious from the code below, I think...
ok will remove this.

Thanks,
-Udipto