# CVE-2021-46986: linux: In the Linux kernel, the following vulnerability has been resolved:  usb: dwc3: gadget: Free gadget structure only af...

CVE-2021-46986 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-46986, released February 28, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-46986
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 28, 2024

## 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().

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.10.38-1 | [DEBIAN-CVE-2021-46986](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46986.md) | Feb 28, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.10.38-1 | [DEBIAN-CVE-2021-46986](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46986.md) | Feb 28, 2024 |
| Linux | linux Debian 14 | 5.10.38-1 | [DEBIAN-CVE-2021-46986](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46986.md) | Feb 28, 2024 |

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