CVE-2026-63929
iio: buffer: Fix DMA fence leak in iio_buffer_enqueue_dmabuf()
Description
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.
INFO
Published Date :
July 19, 2026, 4:17 p.m.
Last Modified :
July 27, 2026, 5:44 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Apply the kernel patch to iio_buffer_enqueue_dmabuf().
- Call dma_fence_put() after dma_resv_add_fence().
- Ensure DMA fence is discarded after signalling.
- Update the Linux kernel.
References to Advisories, Solutions, and Tools
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information, practical solutions, and valuable tools related to
CVE-2026-63929.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63929 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63929
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-63929 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63929 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 19, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f', 'lessThan': '9678aeed8b77d495a417dd057d479f3733094019', 'versionType': 'git'}, {'status': 'affected', 'version': '3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f', 'lessThan': '3412a95afaa5d3262008dfc34f3c7be33d8151dc', 'versionType': 'git'}, {'status': 'affected', 'version': '3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f', 'lessThan': '96cdeaba6a008503455b78a9641c05c2a886a7ec', 'versionType': 'git'}, {'status': 'affected', 'version': '3e26d9f08fbe0b73e951a5e810fdb7a332b7e37f', 'lessThan': 'a093999355084bdbfe6e97f1dd232e58a1525f0b', 'versionType': 'git'}], 'programFiles': ['drivers/iio/industrialio-buffer.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '6.11'}, {'status': 'unaffected', 'version': '0', 'lessThan': '6.11', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.12.93', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.35', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['drivers/iio/industrialio-buffer.c'], 'defaultStatus': 'affected'}] Added Description 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. Added Reference https://git.kernel.org/stable/c/3412a95afaa5d3262008dfc34f3c7be33d8151dc Added Reference https://git.kernel.org/stable/c/9678aeed8b77d495a417dd057d479f3733094019 Added Reference https://git.kernel.org/stable/c/96cdeaba6a008503455b78a9641c05c2a886a7ec Added Reference https://git.kernel.org/stable/c/a093999355084bdbfe6e97f1dd232e58a1525f0b