CVE-2026-93121 (GCVE-0-2026-93121)
Vulnerability from cvelistv5
Published
2026-09-17 16:11
Modified
2026-10-19 09:05
Severity ?
7.0 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths The error paths for endpoint-disabled (ESHUTDOWN) and request-allocation failure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which calls dma_fence_put() on the fence. However, at that point the fence has only been kmalloc'd — dma_fence_init() has not been called yet, so the refcount and the fence ops are uninitialized. Calling dma_fence_put() on such an object leads to undefined behavior. Use kfree() instead, since the fence is just a plain allocation at this stage, and rename the label to err_fence_free to reflect the actual cleanup action.
References
Impacted products
Vendor Product Version
Linux Linux Version: 7b07a2a7ca02a20124b552be96c5a56910795488
Version: 7b07a2a7ca02a20124b552be96c5a56910795488
Version: 7b07a2a7ca02a20124b552be96c5a56910795488
Version: 7b07a2a7ca02a20124b552be96c5a56910795488
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{
  "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": [
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              "lessThan": "be539138d9a187af3b884525a395db10797c64f1",
              "status": "affected",
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              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "7b07a2a7ca02a20124b552be96c5a56910795488",
              "versionType": "git"
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            {
              "lessThan": "58952c83dfe6ea3294a74734d2d1018c1120779a",
              "status": "affected",
              "version": "7b07a2a7ca02a20124b552be96c5a56910795488",
              "versionType": "git"
            },
            {
              "lessThan": "621707dc67c9846fd876d7579ec951d92aa033f1",
              "status": "affected",
              "version": "7b07a2a7ca02a20124b552be96c5a56910795488",
              "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": "6.9"
            },
            {
              "lessThan": "6.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "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": "6.12.110",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.9",
                  "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: Fix fence cleanup in ffs_dmabuf_transfer() error paths\n\nThe error paths for endpoint-disabled (ESHUTDOWN) and request-allocation\nfailure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which\ncalls dma_fence_put() on the fence. However, at that point the fence has\nonly been kmalloc\u0027d \u2014 dma_fence_init() has not been called yet, so the\nrefcount and the fence ops are uninitialized. Calling dma_fence_put() on\nsuch an object leads to undefined behavior.\n\nUse kfree() instead, since the fence is just a plain allocation at this\nstage, and rename the label to err_fence_free to reflect the actual\ncleanup action."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The uninitialized fence is kmalloc\u0027d and then dma_fence_put() in ffs_dmabuf_transfer(), reached only from ffs_epfile_ioctl()\u0027s FUNCTIONFS_DMABUF_TRANSFER case after copy_from_user of usb_ffs_dmabuf_transfer_req; USB host traffic never supplies that ioctl or the fence object.\nAC:H - err_fence_put runs only when epfile-\u003eep != ep after ffs_epfile_wait_ep() (epfile-\u003eep is NULLed solely by ffs_func_eps_disable() from gadget set_alt/disable/unbind) or when usb_ep_alloc_request(..., GFP_ATOMIC) fails; the ioctl caller cannot invoke those gadget callbacks and cannot reliably force that small GFP_ATOMIC allocation to fail.\nPR:L - ffs_epfile_ioctl() has no capable() check; FUNCTIONFS_DMABUF_TRANSFER only needs the endpoint file open. FunctionFS inodes take uid/gid/mode from ffs_fs_parse_param() (uid=/gid=/fmode=), which deployed gadgets use to hand ep nodes to non-root daemons such as adbd.\nUI:N - The attacker issues FUNCTIONFS_DMABUF_TRANSFER themselves on an endpoint fd they already hold; ffs_epfile_wait_ep() needing a prior host SET_CONFIGURATION is ambient gadget enumeration, not a victim action at exploit time.\nS:U - dma_fence_put() on the kmalloc\u0027d ffs_dma_fence runs dma_fence_release() in the same kernel that hosts FunctionFS, so impact stays inside that kernel\u0027s privilege boundary rather than crossing a VM or IOMMU authority.\nC:H - kmalloc_obj(*fence) is not zeroed and dma_fence_init() has not run, so fence-\u003erefcount and fence-\u003eops are leftover heap contents; dma_fence_put() calls dma_fence_release() if the sprayed refcount is 1, which rcu_dereference()s ops and reads other fence fields.\nI:H - dma_fence_release() calls ops-\u003erelease() through the uninitialized fence-\u003eops pointer (or walks garbage cb_list in the pending-signal path); a same-cache heap spray can point ops at attacker-controlled function pointers for control-flow hijack.\nA:H - dma_fence_release() does list_empty(\u0026fence-\u003ecb_list) and dma_fence_lock_irqsave() on uninitialized cb_list/lock and may invoke a wild ops-\u003erelease(), any of which oopses or panics when the ESHUTDOWN or ENOMEM err_fence_put path runs."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:05:54.766Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/be539138d9a187af3b884525a395db10797c64f1"
        },
        {
          "url": "https://git.kernel.org/stable/c/5fd8baacc7dc477df9cac61b45491840247a9b1e"
        },
        {
          "url": "https://git.kernel.org/stable/c/58952c83dfe6ea3294a74734d2d1018c1120779a"
        },
        {
          "url": "https://git.kernel.org/stable/c/621707dc67c9846fd876d7579ec951d92aa033f1"
        }
      ],
      "title": "usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93121",
    "datePublished": "2026-09-17T16:11:27.220Z",
    "dateReserved": "2026-09-17T16:02:15.086Z",
    "dateUpdated": "2026-10-19T09:05:54.766Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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