Medium [CVE-2026-72138] fix error handling in ioctl
This medium-severity Red Hat Linux advisory covers CVE-2026-72138.
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Summary
In the Linux kernel, the following vulnerability has been resolved: xen/gntdev: fix error handling in ioctl When gntdev_ioctl_map_grant_ref() fails to copy the operation result back to userspace after successfully adding the mapping to the list, the error path returns -EFAULT without releasing the reference acquired by gntdev_alloc_map().
The mapping remains in priv->maps with a refcount of 1, causing a memory leak and a dangling list entry. Additionally, gntdev_add_map() may modify map->index to avoid overlap with existing mappings.
Therefore, the index returned to userspace must be obtained after gntdev_add_map() completes. Fix this by holding the mutex across gntdev_add_map(), retrieving the correct index, and copy_to_user().
If copy_to_user() fails, remove the mapping from the list and release the reference while still holding the lock. Fix these issues by properly handling all error cases.
When the `gntdev_ioctl_map_grant_ref()` function fails to copy operation results back to userspace, it does not properly release a memory reference. This oversight can lead to a memory leak and a corrupted list entry.
A local attacker could exploit this to cause a denial of service by exhausting system memory. Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-772.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
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