GHSA-7XV7-RCH9-Q9HW

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-19 18:31
VLAI
Details

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

iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf()

iio_buffer_enqueue_dmabuf() allocates a struct iio_dma_fence (104 bytes, kmalloc-128) via kmalloc_obj()+dma_fence_init(), which sets the initial kref to 1. It then calls dma_resv_add_fence() which takes a second reference (kref=2), and stores a raw pointer in block->fence.

On the success path the function returns without calling dma_fence_put() to release the initial reference, so every buffer enqueue permanently leaks one kmalloc-128 allocation.

The iio_buffer_cleanup() work item only releases the temporary reference taken during completion signalling by iio_buffer_signal_dmabuf_done(); the initial reference from dma_fence_init() is never released.

With four iio_rwdev instances at 240kHz and 512 samples per buffer, this produces ~1875 kmalloc-128 allocations per second matching the observed slab growth exactly. A test with ftrace confirmed that the dma_fence_destroy event was never triggered.

Fix by calling dma_fence_put() after dma_resv_add_fence(), transferring ownership of the fence to the DMA reservation object. The DMA fence then gets properly discarded after being signalled.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-63929"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:11Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\niio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf()\n\niio_buffer_enqueue_dmabuf() allocates a struct iio_dma_fence (104 bytes,\nkmalloc-128) via kmalloc_obj()+dma_fence_init(), which sets the initial\nkref to 1.  It then calls dma_resv_add_fence() which takes a second\nreference (kref=2), and stores a raw pointer in block-\u003efence.\n\nOn the success path the function returns without calling dma_fence_put()\nto release the initial reference, so every buffer enqueue permanently\nleaks one kmalloc-128 allocation.\n\nThe iio_buffer_cleanup() work item only releases the temporary reference\ntaken during completion signalling by iio_buffer_signal_dmabuf_done();\nthe initial reference from dma_fence_init() is never released.\n\nWith four iio_rwdev instances at 240kHz and 512 samples per buffer,\nthis produces ~1875 kmalloc-128 allocations per second matching the\nobserved slab growth exactly. A test with ftrace confirmed that the\ndma_fence_destroy event was never triggered.\n\nFix by calling dma_fence_put() after dma_resv_add_fence(), transferring\nownership of the fence to the DMA reservation object. The DMA fence then\ngets properly discarded after being signalled.",
  "id": "GHSA-7xv7-rch9-q9hw",
  "modified": "2026-07-19T18:31:46Z",
  "published": "2026-07-19T18:31:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63929"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3412a95afaa5d3262008dfc34f3c7be33d8151dc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9678aeed8b77d495a417dd057d479f3733094019"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/96cdeaba6a008503455b78a9641c05c2a886a7ec"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a093999355084bdbfe6e97f1dd232e58a1525f0b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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