CVE-2021-46986: In the Linux kernel, the following vulnerability has been resolved: usb: dwc3: gadget: Free gadget structure only after freeing endpoints As part of...

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().

Metrics

CVSS 3.1

5.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.23%

13.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions	Update
Linux	Linux Kernel	>= 5.10, < 5.10.38	—
Linux	Linux Kernel	>= 5.11, < 5.11.22	—
Linux	Linux Kernel	>= 5.12, < 5.12.5	—
Linux	Linux Kernel	5.13	Rc1

References

Timeline

Published: Feb 28, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-46986?

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().

How severe is CVE-2021-46986?

CVE-2021-46986 has a CVSS score of 5.5/10 (MEDIUM severity). The EPSS model estimates a 0.23% probability of exploitation in the next 30 days.

How do I fix CVE-2021-46986?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.