high CVSS 7.8

CVE-2022-48991·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables.

Severity
high
Software
Kernel
Fixed in
6.0.13
Published
2024-10-21

Affected versions

From: 5.16

Until: 6.0.13

Fixed in: 6.0.13

How to fix this CVE

Update your Linux kernel to version 6.0.13 or later to patch the MMU notifier vulnerability in the khugepaged subsystem. This vulnerability affects kernel versions 5.16 through 6.0.12 and can lead to use-after-free conditions when secondary MMUs (such as KVM) fail to receive proper notifications during transparent huge page collapse operations. Ensure all systems running affected kernels are updated immediately, particularly those hosting virtualized workloads.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Run 'uname -r' to check your current kernel version and verify if it falls within the affected range (5.16.x to 6.0.12)
  2. Execute 'grep -i khugepaged /boot/config-$(uname -r)' to confirm that transparent huge page collapse is enabled in your kernel configuration
  3. Check for KVM/virtualization workloads with 'ps aux | grep -E "qemu|libvirtd"' to identify systems where secondary MMU impact is highest
  4. After patching, run 'uname -r' again and verify the new kernel version is 6.0.13 or higher, then reboot if kernel was updated

FAQ

What is CVE-2022-48991?

This vulnerability is a memory safety issue in the Linux kernel's khugepaged subsystem where MMU notifiers are not properly invoked during transparent huge page collapse operations on shmem and file-backed pages. This allows secondary MMUs like KVM to continue accessing pages that have been unmapped, creating a use-after-free condition.

Is CVE-2022-48991 being actively exploited?

No, CVE-2022-48991 is not listed on CISA's Known Exploited Vulnerabilities catalog and there are no public exploits available. However, its high CVSS score of 7.8 and local attack vector mean it should still be prioritized for patching, especially in multi-tenant virtualization environments.

What versions of Kernel are affected by CVE-2022-48991?

Linux kernel versions 5.16.0 through 6.0.12 are affected. The vulnerability was introduced in commit f3f0e1d2150b but gained significant impact starting with commit 27e1f8273113. Kernel version 6.0.13 and all later versions contain the fix.

How do I check if my server is vulnerable to CVE-2022-48991?

Run 'uname -r' to display your kernel version. If the output shows a version between 5.16.0 and 6.0.12 (e.g., 5.19.10 or 6.0.5), your system is vulnerable. Additionally, check if CONFIG_TRANSPARENT_HUGEPAGE=y is enabled with 'grep TRANSPARENT_HUGEPAGE /boot/config-$(uname -r)'.

Does Defensia detect CVE-2022-48991?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel package is installed on a monitored server, CVE-2022-48991 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
CVE-2024-39462CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: clk: bcm: dvp: Assign ->num before accessing ->hws Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by") annotated the hws member of 'struct clk_hw_onecell_data' with __counted_by, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in clk_dvp_probe() due to ->num being assigned after ->hws has been accessed: UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2 index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]') Move the ->num initialization to before the first access of ->hws, which clears up the warning.
CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
CVE-2021-47378CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nvme-rdma: destroy cm id before destroy qp to avoid use after free We should always destroy cm_id before destroy qp to avoid to get cma event after qp was destroyed, which may lead to use after free. In RDMA connection establishment error flow, don't destroy qp in cm event handler.Just report cm_error to upper level, qp will be destroy in nvme_rdma_alloc_queue() after destroy cm id.
CVE-2024-36031CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: keys: Fix overwrite of key expiration on instantiation The expiry time of a key is unconditionally overwritten during instantiation, defaulting to turn it permanent. This causes a problem for DNS resolution as the expiration set by user-space is overwritten to TIME64_MAX, disabling further DNS updates. Fix this by restoring the condition that key_set_expiry is only called when the pre-parser sets a specific expiry.

References

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