Description

In the Linux kernel, the following vulnerability has been resolved:

usb: musb: Fix hardware lockup on first Rx endpoint request

There is a possibility that a request's callback could be invoked from
usb_ep_queue() (call trace below, supplemented with missing calls):

req->complete from usb_gadget_giveback_request
(drivers/usb/gadget/udc/core.c:999)
usb_gadget_giveback_request from musb_g_giveback
(drivers/usb/musb/musb_gadget.c:147)
musb_g_giveback from rxstate
(drivers/usb/musb/musb_gadget.c:784)
rxstate from musb_ep_restart
(drivers/usb/musb/musb_gadget.c:1169)
musb_ep_restart from musb_ep_restart_resume_work
(drivers/usb/musb/musb_gadget.c:1176)
musb_ep_restart_resume_work from musb_queue_resume_work
(drivers/usb/musb/musb_core.c:2279)
musb_queue_resume_work from musb_gadget_queue
(drivers/usb/musb/musb_gadget.c:1241)
musb_gadget_queue from usb_ep_queue
(drivers/usb/gadget/udc/core.c:300)

According to the docstring of usb_ep_queue(), this should not happen:

"Note that @req's ->complete() callback must never be called from within
usb_ep_queue() as that can create deadlock situations."

In fact, a hardware lockup might occur in the following sequence:

1. The gadget is initialized using musb_gadget_enable().
2. Meanwhile, a packet arrives, and the RXPKTRDY flag is set, raising an
interrupt.
3. If IRQs are enabled, the interrupt is handled, but musb_g_rx() finds an
empty queue (next_request() returns NULL). The interrupt flag has
already been cleared b...

Classification

CVE ID: CVE-2024-56687

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.08% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

https://git.kernel.org/stable/c/c749500b28cae67410792096133ee7f282439c51
https://git.kernel.org/stable/c/5906ee3693674d734177df13a519a21bb03f730d
https://git.kernel.org/stable/c/f05ad9755bb294328c3d0f429164ac6d4d08c548
https://git.kernel.org/stable/c/0c89445e6d475b78d37b64ae520831cd43af7db4
https://git.kernel.org/stable/c/3fc137386c4620305bbc2a216868c53f9245670a

Timeline