CVE-2026-31578

Description

In the Linux kernel, the following vulnerability has been resolved: media: as102: fix to not free memory after the device is registered in as102_usb_probe() In as102_usb driver, the following race condition occurs: ``` CPU0 CPU1 as102_usb_probe() kzalloc(); // alloc as102_dev_t .... usb_register_dev(); fd = sys_open("/path/to/dev"); // open as102 fd .... usb_deregister_dev(); .... kfree(); // free as102_dev_t .... sys_close(fd); as102_release() // UAF!! as102_usb_release() kfree(); // DFB!! ``` When a USB character device registered with usb_register_dev() is later unregistered (via usb_deregister_dev() or disconnect), the device node is removed so new open() calls fail. However, file descriptors that are already open do not go away immediately: they remain valid until the last reference is dropped and the driver's .release() is invoked. In as102, as102_usb_probe() calls usb_register_dev() and then, on an error path, does usb_deregister_dev() and frees as102_dev_t right away. If userspace raced a successful open() before the deregistration, that open FD will later hit as102_release() --> as102_usb_release() and access or free as102_dev_t again, occur a race to use-after-free and double-free vuln. The fix is to never kfree(as102_dev_t) directly once usb_register_dev() has succeeded. After deregistration, defer freeing memory to .release(). In other words, let release() perform the last kfree when the final open FD is closed.

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://git.kernel.org/stable/c/09e9206008b887aa553733bd915d73131071a086
• https://git.kernel.org/stable/c/2eeae47a438694408189138048a786be99954032
• https://git.kernel.org/stable/c/582fbecb3756330006fe1950762412a68c2cacd2
• https://git.kernel.org/stable/c/7e5aedf6059cba2a669d86caeaf5a51f33ec85a1
• https://git.kernel.org/stable/c/8bd29dbe03fc5b0f039ab2395ff37b64236d2f0c
• https://git.kernel.org/stable/c/cb8092038e95dc1113a68e63762de40fff61ba71
• https://www.suse.com/security/cve/CVE-2026-31578.html
• https://security-tracker.debian.org/tracker/CVE-2026-31578

CWEs

CWE-416