CVE-2022-49989 in Linux
Summary
by MITRE • 06/18/2025
In the Linux kernel, the following vulnerability has been resolved:
xen/privcmd: fix error exit of privcmd_ioctl_dm_op()
The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() potentially with pages being NULL, leading to a NULL dereference.
Additionally lock_pages() doesn't check for pin_user_pages_fast() having been completely successful, resulting in potentially not locking all pages into memory. This could result in sporadic failures when using the related memory in user mode.
Fix all of that by calling unlock_pages() always with the real number of pinned pages, which will be zero in case pages being NULL, and by checking the number of pages pinned by pin_user_pages_fast() matching the expected number of pages.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 01/16/2026
The vulnerability described in CVE-2022-49989 resides within the Linux kernel's Xen hypervisor subsystem, specifically affecting the privcmd driver's handling of device model operations. This issue manifests in the privcmd_ioctl_dm_op() function which manages communication between guest operating systems and hypervisor device models. The flaw represents a critical security concern as it involves improper memory management during privilege escalation operations that could potentially be exploited by malicious actors to compromise system integrity.
The technical root cause of this vulnerability stems from two interconnected memory management errors within the kernel's Xen support code. The first issue occurs when the function attempts to call unlock_pages() with potentially NULL page pointers, creating a null pointer dereference condition that could crash the kernel or potentially be exploited for privilege escalation. The second problem arises from insufficient validation of the pin_user_pages_fast() function's return value, which fails to verify whether all requested pages were successfully locked into memory. This incomplete page locking can result in memory access violations and system instability when user-space applications attempt to access the affected memory regions.
The operational impact of this vulnerability extends beyond simple system crashes, as it creates conditions that could enable attackers to exploit memory management inconsistencies in virtualized environments. When the kernel fails to properly validate page pinning operations, it creates potential race conditions and memory access violations that could be leveraged to escape virtual machine isolation boundaries. This particular flaw affects systems running the Linux kernel with Xen hypervisor support, particularly those utilizing device model operations for hardware virtualization. The sporadic nature of the failures makes this vulnerability particularly dangerous as it may not manifest consistently, allowing attackers to potentially exploit the memory management inconsistencies without immediate detection.
The fix implemented addresses both aspects of the memory management flaw by ensuring that unlock_pages() is always called with the correct number of pinned pages, including handling the edge case where pages might be NULL. Additionally, the solution requires explicit validation of the pin_user_pages_fast() function's return value to confirm that the expected number of pages were successfully pinned into memory. This approach aligns with security best practices for kernel memory management and follows the principle of least privilege by ensuring proper resource cleanup and validation. The mitigation strategy prevents both the null pointer dereference and the incomplete page locking scenarios that could lead to system instability or potential privilege escalation.
This vulnerability demonstrates characteristics consistent with CWE-476_NULL_Pointer_Dereference and CWE-129_Invalid_Storage_Size, while also exhibiting behaviors related to privilege escalation and memory corruption patterns. From an ATT&CK perspective, this vulnerability could potentially be leveraged as part of a privilege escalation technique, specifically targeting the kernel's memory management subsystem to gain elevated privileges. The fix ensures proper error handling and resource management in kernel space operations, which is critical for maintaining the integrity of virtualized environments and preventing potential exploitation through memory corruption attacks. Organizations running Xen-based virtualization environments should prioritize applying this kernel patch to prevent potential exploitation of these memory management flaws.