CVE-2025-38681

In the Linux kernel, the following vulnerability has been resolved:

mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd()

Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful.

But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems.

To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables.

Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, lets just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios.

Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/1636b5e9c3543b87d673e32a47e7c18698882425
• https://git.kernel.org/stable/c/3ee9a8c27bfd72c3f465004fa8455785d61be5e8
• https://git.kernel.org/stable/c/59305202c67fea50378dcad0cc199dbc13a0e99a
• https://git.kernel.org/stable/c/67995d4244694928ce701928e530b5b4adeb17b4
• https://git.kernel.org/stable/c/69bea84b06b5e779627e7afdbf4b60a7d231c76f
• https://git.kernel.org/stable/c/ac25ec5fa2bf6e606dc7954488e4dded272fa9cd
• https://git.kernel.org/stable/c/ca8c414499f2e5337a95a76be0d21b728ee31c6b
• https://git.kernel.org/stable/c/ff40839e018b82c4d756d035f34a63aa2d93be83
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html