CVE-2026-43128: RDMA/umem: Fix double dma_buf_unpin in failure path
In the Linux kernel, the following vulnerability has been resolved:
RDMA/umem: Fix double dmabufunpin in failure path
In ibumemdmabufgetpinnedwithdmadevice(), the call to ibumemdmabufmappages() can fail. If this occurs, the dmabuf is immediately unpinned but the umemdmabuf->pinned flag is still set. Then, when ibumemrelease() is called, it calls ibumemdmabufrevoke() which will call dmabufunpin() again.
Fix this by removing the immediate unpin upon failure and just let the ibumemrelease/revoke path handle it. This also ensures the proper unmap-unpin unwind ordering if the dmabufmappages call happened to fail due to dmaresvwaittimeout (and therefore has a non-NULL umemdmabuf->sgt).
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.85-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.116-1Fixed in 7.2.15-1Fixed in 7.3.4-1 - Compensating control
Remove the immediate dma_buf_unpin() call from the ib_umem_dmabuf_get_pinned_with_dma_device() failure path after ib_umem_dmabuf_map_pages() fails; let the ib_umem_release()/ib_umem_dmabuf_revoke() path perform the unmap-unpin cleanup.
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The CVSS vector indicates local access and low privileges are required. No user interaction is required.
Which component and operation are implicated?
The issue is in the Linux kernel RDMA umem dma-buf handling path, specifically when ib_umem_dmabuf_map_pages() fails during ib_umem_dmabuf_get_pinned_with_dma_device().
What happens when the vulnerable failure path is reached?
A failed page-mapping call can cause the dma-buf to be unpinned immediately while its pinned flag remains set. Subsequent release processing can unpin it again, resulting in a double unpin and incorrect cleanup ordering.
How does the fix change failure handling?
The fix removes the immediate unpin after the mapping failure and leaves cleanup to the ib_umem_release and revoke path. This also preserves the required unmap-before-unpin ordering when a scatter-gather table exists.