CVE-2026-89732 (GCVE-0-2026-89732)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-19 08:51
Severity ?
Summary
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
Version: ddf8abd2599491cbad959c700b90ba72a5dce8d0
 Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "fbe3db4b650c284df8eb4cb68eebcf270cf861b5",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "30430509c156e1df2bdafd5f1cadb160e53db5d6",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "bafddd0f20b5228760be303aa69c58502e92309c",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "b0a6bfac0c3c3edf5b2ecaee87a09234601fe78d",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "fd20cc68bbdb5620696ac108e8f2efd180fe2c1a",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "34e88f53614640b59039a46717fb6142e9871022",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "eac233e63f9db82ba874e3cccafaafab162999e0",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            },
            {
              "lessThan": "569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082",
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.35"
            },
            {
              "lessThan": "2.6.35",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.270",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.221",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.188",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Prevent deadlock during ep0 read loop\n\nCurrently, ffs_ep0_read() holds ffs-\u003emutex when it prepares to go to\nsleep waiting for an event. When no setup events are pending, it calls\nwait_event_interruptible_exclusive_locked_irq() with the mutex still\nheld. The wait macro deliberately drops the waitqueue spinlock before\nsleeping but does not drop the mutex.\n\nIf a userspace daemon is polling ep0 via read() and the gadget is\nasynchronously torn down via configfs (e.g., echo \"\" \u003e UDC), a\ndeadlock can occur:\n\n1. The configfs teardown calls functionfs_unbind(), which queues a\n   FUNCTIONFS_UNBIND event.\n2. The daemon wakes up, consumes the event, and drops the mutex.\n3. However, if the daemon loops and immediately issues another read()\n   before exiting, it reacquires ffs-\u003emutex and again goes into an\n   interruptible sleep.\n4. Meanwhile, functionfs_unbind() continues execution and attempts to\n   acquire ffs-\u003emutex to tear down ep0req.\n5. The kernel deadlocks because the configfs thread is stuck in an\n   uninterruptible sleep waiting for the mutex, while the userspace\n   daemon is in an interruptible sleep holding the mutex forever\n   because no more events will arrive.\n\nTo fix this, we drop both the waitqueue spinlock and ffs-\u003emutex before\ngoing to sleep, and use wait_event_interruptible_exclusive() instead.\nUpon waking up, we jump back to the `retry` label to safely reacquire\nthe mutex and re-evaluate the state machine. By not sleeping with\nffs-\u003emutex held, we natively decouple gadget teardowns (which require\nthe mutex) from userspace polling."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:51:45.542Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fbe3db4b650c284df8eb4cb68eebcf270cf861b5"
        },
        {
          "url": "https://git.kernel.org/stable/c/30430509c156e1df2bdafd5f1cadb160e53db5d6"
        },
        {
          "url": "https://git.kernel.org/stable/c/bafddd0f20b5228760be303aa69c58502e92309c"
        },
        {
          "url": "https://git.kernel.org/stable/c/b0a6bfac0c3c3edf5b2ecaee87a09234601fe78d"
        },
        {
          "url": "https://git.kernel.org/stable/c/fd20cc68bbdb5620696ac108e8f2efd180fe2c1a"
        },
        {
          "url": "https://git.kernel.org/stable/c/34e88f53614640b59039a46717fb6142e9871022"
        },
        {
          "url": "https://git.kernel.org/stable/c/eac233e63f9db82ba874e3cccafaafab162999e0"
        },
        {
          "url": "https://git.kernel.org/stable/c/569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082"
        }
      ],
      "title": "usb: gadget: f_fs: Prevent deadlock during ep0 read loop",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89732",
    "datePublished": "2026-09-11T19:46:41.974Z",
    "dateReserved": "2026-09-11T19:38:34.760Z",
    "dateUpdated": "2026-10-19T08:51:45.542Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.