CVE-2026-31721

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_hid: move list and spinlock inits from bind to alloc There was an issue when you did the following: - setup and bind an hid gadget - open /dev/hidg0 - use the resulting fd in EPOLL_CTL_ADD - unbind the UDC - bind the UDC - use the fd in EPOLL_CTL_DEL When CONFIG_DEBUG_LIST was enabled, a list_del corruption was reported within remove_wait_queue (via ep_remove_wait_queue). After some debugging I found out that the queues, which f_hid registers via poll_wait were the problem. These were initialized using init_waitqueue_head inside hidg_bind. So effectively, the bind function re-initialized the queues while there were still items in them. The solution is to move the initialization from hidg_bind to hidg_alloc to extend their lifetimes to the lifetime of the function instance. Additionally, I found many other possibly problematic init calls in the bind function, which I moved as well.

References

• https://git.kernel.org/stable/c/13440c0db227c5db01da751ed966dde4cdd2ea18
• https://git.kernel.org/stable/c/26a879a41ed960b3fb4ec773ef2788c515c0e488
• https://git.kernel.org/stable/c/4e0a88254ad59f6c53a34bf5fa241884ec09e8b2
• https://git.kernel.org/stable/c/5d1bb391ceeebb28327703dd07af8c6324af298f
• https://git.kernel.org/stable/c/81aee4500055876883658b024b6fb61801afe134