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CVE-2026-89732— usb: gadget: f_fs: Prevent deadlock during ep0 read loop

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，已修复以下漏洞： usb: gadget: f_fs: 防止 ep0 读取循环中的死锁 当前， 在准备进入睡眠状态等待事件时，仍持有 互斥锁。当没有待处理的 setup 事件时，它在仍持有互斥锁的情况下调用了 。该 wait 宏在进入睡眠前会主动释放等待队列的自旋锁，但不会释放互斥锁。 如果用户空间守护进程通过 轮询 ep0，而 gadget 设备通过 configfs 被异步解绑（例如执行 ），则可能发生死锁： 1. configfs 的解绑流程调用 ，该函数会入队一个 事件。 2. 守护

AI Predicted 5.5 Difficulty: Moderate

Possible ATT&CK Techniques 1 AI

T1027 · Obfuscated Files or Information

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux ddf8abd2599491cbad959c700b90ba72a5dce8d0< fd20cc68bbdb5620696ac108e8f2efd180fe2c1a affected
ddf8abd2599491cbad959c700b90ba72a5dce8d0< 34e88f53614640b59039a46717fb6142e9871022 affected
ddf8abd2599491cbad959c700b90ba72a5dce8d0< eac233e63f9db82ba874e3cccafaafab162999e0 affected
ddf8abd2599491cbad959c700b90ba72a5dce8d0< 569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082 affected
2.6.35 affected
< 2.6.35 unaffected
6.12.109≤ 6.12.* unaffected
6.18.50≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-89732

Vulnerability Information
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Vulnerability Title
usb: gadget: f_fs: Prevent deadlock during ep0 read loop
Source: CVE Program / CVE List V5
Vulnerability Description
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: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux ddf8abd2599491cbad959c700b90ba72a5dce8d0 ~ fd20cc68bbdb5620696ac108e8f2efd180fe2c1a -
Linux Linux 2.6.35 -

II. Public POCs for CVE-2026-89732

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III. Intelligence Information for CVE-2026-89732

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Patches & Fixes for CVE-2026-89732 (4)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89491 ocfs2: cluster: don't sleep while holding o2hb_live_lock in o2hb_region_pin()
CVE-2026-89477 sctp: fix NULL deref on untransmitted RECONF completion
CVE-2026-89478 sctp: drop a chunk if its transport was removed
CVE-2026-89479 sctp: stop processing a packet once its association is deleted
CVE-2026-89480 nvme-tcp: reject a read that transferred too few bytes
CVE-2026-89482 nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89481 nvme-tcp: fix host memory disclosure on R2T for a read command
CVE-2026-89483 nvme: zero the discard fallback page
CVE-2026-89484 lockd: fix NULL dereference on lockowner allocation failure
CVE-2026-89485 lockd: pin next file across nlm_inspect_file lock-drop
CVE-2026-89486 ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user()
CVE-2026-89487 openvswitch: only skb_tx_error() a packet we are about to drop
CVE-2026-89488 openvswitch: Fix CT limit teardown use-after-free
CVE-2026-89489 openrisc: fix arbitrary kernel memory access via or1k_atomic syscall
CVE-2026-89500 ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page
CVE-2026-89497 orangefs: skip leading spaces before parsing client debug masks
CVE-2026-89498 orangefs: fix double-free of trailer_buf on readdir copy failure
CVE-2026-89499 ring-buffer: Stop remote reader update when page swap fails
CVE-2026-89496 ocfs2: always run deallocs on copy-on-write completion
CVE-2026-89501 ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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