{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-63929",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2026-63929"
  ],
  "published": "2026-07-19T14:56:29Z",
  "summary": "iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf()",
  "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->fence.\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.",
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      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63929"
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    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-07-19T14:56:29Z"
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}