CVE-2026-72138xen/gntdev: fix error handling in ioctl

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/52dc40ef0cfee6ae89b7524967e73f0ba37906d7
• https://git.kernel.org/stable/c/1dd9cb98fe228e017fff9efb33862ff38c741b65
• https://git.kernel.org/stable/c/6df926130aee6cab9b5d2e5b7862e49ccac348dc
• https://git.kernel.org/stable/c/311011f8cc206c5af2877b03e3f627ee1b8fe024
• https://git.kernel.org/stable/c/18a693733f7ad004e1ab0466693121ca70cd95dd
• https://git.kernel.org/stable/c/16d3ccdabb8dee9be2cdcd6d3f9a125572ec0454
• https://git.kernel.org/stable/c/6883269a323609f68f6faa903f8f8ff3d191cec8
• https://git.kernel.org/stable/c/45ca1afe2fd14c04e37227e79d3f8455831d8408