CVE-2026-89732

CVE CVE-2026-89732EUVD EUVD-2026-76644Published 2026-09-11T19:46:41.000ZLast changed 2026-09-14T12:02:20.000Z

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Prevent deadlock during ep0 read loop Currently, ffs_ep0_read() holds ffs->mutex when it prepares to go to sleep waiting for an event. When no setup events are pending, it calls wait_event_interruptible_exclusive_locked_irq() with the mutex still held. The wait macro deliberately drops the waitqueue spinlock before sleeping but does not drop the mutex. If a userspace daemon is polling ep0 via read() and the gadget is asynchronously torn down via configfs (e.g., echo "" > UDC), a deadlock can occur: 1. The configfs teardown calls functionfs_unbind(), which queues a FUNCTIONFS_UNBIND event. 2. The daemon wakes up, consumes the event, and drops the mutex. 3. However, if the daemon loops and immediately issues another read() before exiting, it reacquires ffs->mutex and again goes into an interruptible sleep. 4. Meanwhile, functionfs_unbind() continues execution and attempts to acquire ffs->mutex to tear down ep0req. 5. The kernel deadlocks because the configfs thread is stuck in an uninterruptible sleep waiting for the mutex, while the userspace daemon is in an interruptible sleep holding the mutex forever because no more events will arrive. To fix this, we drop both the waitqueue spinlock and ffs->mutex before going to sleep, and use wait_event_interruptible_exclusive() instead. Upon waking up, we jump back to the `retry` label to safely reacquire the mutex and re-evaluate the state machine. By not sleeping with ffs->mutex held, we natively decouple gadget teardowns (which require the mutex) from userspace polling.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux ddf8abd2599491cbad959c700b90ba72a5dce8d0 <fd20cc68bbdb5620696ac108e8f2efd180fe2c1a; patch: 5.10.270; patch: 6.1.188; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <fbe3db4b650c284df8eb4cb68eebcf270cf861b5; patch: 0; patch: 6.6.157; 2.6.35; patch: 6.12.109; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <b0a6bfac0c3c3edf5b2ecaee87a09234601fe78d; patch: 6.18.50; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <bafddd0f20b5228760be303aa69c58502e92309c; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <34e88f53614640b59039a46717fb6142e9871022; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <30430509c156e1df2bdafd5f1cadb160e53db5d6; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082; patch: 7.2.4; patch: 5.15.221; ddf8abd2599491cbad959c700b90ba72a5dce8d0 <eac233e63f9db82ba874e3cccafaafab162999e0; patch: 7.3-rc1

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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