CVE-2022-49172
Published: 26 February 2025
Description
In the Linux kernel, the following vulnerability has been resolved: parisc: Fix non-access data TLB cache flush faults When a page is not present, we get non-access data TLB faults from the fdc and fic instructions in flush_user_dcache_range_asm and flush_user_icache_range_asm. When these occur, the cache line is not invalidated and potentially we get memory corruption. The problem was hidden by the nullification of the flush instructions. These faults also affect performance. With pa8800/pa8900 processors, there will be 32 faults per 4 KB page since the cache line is 128 bytes. There will be more faults with earlier processors. The problem is fixed by using flush_cache_pages(). It does the flush using a tmp alias mapping. The flush_cache_pages() call in flush_cache_range() flushed too large a range. V2: Remove unnecessary preempt_disable() and preempt_enable() calls.
Security Summary
CVE-2022-49172 is a vulnerability in the Linux kernel's PA-RISC (parisc) architecture implementation, specifically affecting the flush_user_dcache_range_asm and flush_user_icache_range_asm functions. When flushing cache ranges for pages that are not present, non-access data TLB faults occur from fdc and fic instructions, preventing proper cache line invalidation and leading to potential memory corruption. This issue was masked by nullification of the flush instructions but also caused performance degradation, with up to 32 faults per 4 KB page on pa8800/pa8900 processors due to 128-byte cache lines. Additionally, flush_cache_range() flushed excessively large ranges.
A local attacker with low privileges (AV:L/AC:L/PR:L/UI:N) can exploit this vulnerability to trigger the faulty cache flushes, resulting in memory corruption. The CVSS v3.1 base score of 7.1 reflects high impact on integrity (I:H) and availability (A:H) with no confidentiality impact (C:N), potentially enabling denial-of-service or further privilege escalation through corrupted memory states in user space cache operations.
Mitigation requires applying stable kernel patches, as detailed in the referenced commits: b3d6adb3a49d82e4e557c5fc16f50c9ff731da5d, ddca4b82027e2a66333dd40fab21a4beff435c7e, and f839e5f1cef36ce268950c387129b1bfefdaebc9. These replace the faulty flush instructions with flush_cache_pages(), which uses a temporary alias mapping for safe flushing, corrects the range in flush_cache_range(), and removes unnecessary preempt_disable/enable calls in version 2 of the patch.
Details
- CWE(s)