NuytsTech Security

CVE-2026-31721

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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.

More information : https://git.kernel.org/stable/c/13440c0db227c5db01da751ed966dde4cdd2ea18

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