title: usb: dwc3: gadget: Free gadget structure only after freeing endpoints
description: In the Linux kernel, the following vulnerability has been resolved:
usb: dwc3: gadget: Free gadget structure only after freeing endpoints
As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
dynamically") the dwc3_gadget_release() was added which will free
the dwc->gadget structure upon the device's removal when
usb_del_gadget_udc() is called in dwc3_gadget_exit().
However, simply freeing the gadget results a dangling pointer
situation: the endpoints created in dwc3_gadget_init_endpoints()
have their dep->endpoint.ep_list members chained off the list_head
anchored at dwc->gadget->ep_list.  Thus when dwc->gadget is freed,
the first dwc3_ep in the list now has a dangling prev pointer and
likewise for the next pointer of the dwc3_ep at the tail of the list.
The dwc3_gadget_free_endpoints() that follows will result in a
use-after-free when it calls list_del().
This was caught by enabling KASAN and performing a driver unbind.
The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
callback for dwc3") also exposes this as a panic during shutdown.
There are a few possibilities to fix this.  One could be to perform
a list_del() of the gadget->ep_list itself which removes it from
the rest of the dwc3_ep chain.
Another approach is what this patch does, by splitting up the
usb_del_gadget_udc() call into its separate "del" and "put"
components.  This allows dwc3_gadget_free_endpoints() to be
called before the gadget is finally freed with usb_put_gadget().
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: e81a7018d93a, lessThan: 1ea775021282, status: affected, versionType: git
version: e81a7018d93a, lessThan: bc0cdd724932, status: affected, versionType: git
version: e81a7018d93a, lessThan: b4b8e9601d7e, status: affected, versionType: git
version: e81a7018d93a, lessThan: bb9c74a5bd14, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 5.10, status: affected
version: 0, lessThan: 5.10, status: unaffected, versionType: custom
version: 5.10.38, lessThanOrEqual: 5.10.*, status: unaffected, versionType: custom
version: 5.11.22, lessThanOrEqual: 5.11.*, status: unaffected, versionType: custom
version: 5.12.5, lessThanOrEqual: 5.12.*, status: unaffected, versionType: custom
version: 5.13, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
