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

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Summary

CVECVE-2026-63929
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:11 UTC
Updated2026-07-19 16:17:11 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.002000000 probability, percentile 0.100170000 (date 2026-07-20)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f 9678aeed8b77d495a417dd057d479f3733094019 git Not specified
CNA Linux Linux affected 3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f 3412a95afaa5d3262008dfc34f3c7be33d8151dc git Not specified
CNA Linux Linux affected 3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f 96cdeaba6a008503455b78a9641c05c2a886a7ec git Not specified
CNA Linux Linux affected 3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f a093999355084bdbfe6e97f1dd232e58a1525f0b git Not specified
CNA Linux Linux affected 6.11 Not specified
CNA Linux Linux unaffected 6.11 semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/96cdeaba6a008503455b78a9641c05c2a886a7ec 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a093999355084bdbfe6e97f1dd232e58a1525f0b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3412a95afaa5d3262008dfc34f3c7be33d8151dc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9678aeed8b77d495a417dd057d479f3733094019 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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