Bug 2516334 (CVE-2026-72138)

Summary: CVE-2026-72138 kernel: xen/gntdev: fix error handling in ioctl
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the `xen/gntdev` component of the Linux kernel. 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.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-15 06:07:05 UTC 
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.
Comment 1 gkamathe 2026-08-18 06:49:02 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081531-CVE-2026-72138-5d33@gregkh/T