CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's handling of unaligned addresses in the `huge_ptep_get()` function, which can lead to incorrect mapping of hugetlb folios and potentially cause kernel panics due to dereferencing invalid memory. Systems with a page size of 16K are particularly at risk, as they may experience excessive kernel workload and instability from incorrect A/D bit collection. Administrators of Linux systems, especially those utilizing hugetlb pages, should prioritize applying the fix to mitigate these risks.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: arm64: make huge_ptep_get handled unaligned addresses huge_ptep_get() can be handed a virtual address pointing to the middle of a contpmd/contpte mapped hugetlb folio (examples of callers are pagemap_hugetlb_range, page_mapped_in_vma). The arm64 helper rewalks the pgtables in find_num_contig to answer whether the huge pte we have maps a contpmd or a contpte hugetlb folio, and returns CONT_PMDS or CONT_PTES, so that it can collect a/d bits over the contiguous ptes. We can falsely return CONT_PTES instead of CONT_PMDS if the addr is not aligned. On systems where CONT_PTES != CONT_PMDS (meaning page size is 16K), we could collect excess A/D bit state, meaning extra work for the kernel. Even worse, we may iterate beyond the PTE table and dereference a garbage ptep pointer to access physical memory we don't own. Since the ptep pointer is a linear map address, we may run off the end of the linear map or into a hole, dereference a VA not mapped into the kernel pgtables and cause kernel panic. Fix this by aligning the pmdp pointer down to a contpmd base before checking equality with the passed huge pte pointer, to correctly answer whether the huge pte is the base of a contpmd block.