On Thu, Jan 04, 2024 at 02:13:51PM +0100, Greg Kroah-Hartman wrote:By the commit description of lvstest driver this seems to be the procedure:
On Thu, Jan 04, 2024 at 06:35:38PM +0530, Udipto Goswami wrote:
Hi Greg,
On 1/4/2024 4:14 PM, Greg Kroah-Hartman wrote:
On Thu, Jan 04, 2024 at 03:56:16PM +0530, Udipto Goswami wrote:
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.
Is this true for any real (or fake) hardware?
We saw this in our QCOM hardwares where lvstest.c was calling
get_dev_desc_store:
usb_set_device_state+0x128/0x17c
create_lvs_device+0x60/0xf8 [lvstest]
get_dev_desc_store+0x94/0x18c [lvstest]
dev_attr_store+0x30/0x48
I think the part of the test procedure is to first unbind the hub driver
which calls hub_disconnect setting the maxchild = 0.
Are you sure lvstest is correct here?
Thanks for the review Alan. Sure I'll put a comment here stating the necessity of the check for clarity in the next version.
This is what happens when people work behind the hub driver's back. :-(
If you can't find another way to fix the problem, you should at least
change the patch to include a comment before the "if (hub)" test,
explaining why it is necessary. Otherwise somebody in the future will
remove the test, because under normal circumstances hub would never be
NULL here.