Vulnerability CVE-2024-40948
Published: 2024-07-12

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

mm/page_table_check: fix crash on ZONE_DEVICE

Not all pages may apply to pgtable check. One example is ZONE_DEVICE
pages: they map PFNs directly, and they don't allocate page_ext at all
even if there's struct page around. One may reference
devm_memremap_pages().

When both ZONE_DEVICE and page-table-check enabled, then try to map some
dax memories, one can trigger kernel bug constantly now when the kernel
was trying to inject some pfn maps on the dax device:

kernel BUG at mm/page_table_check.c:55!

While it's pretty legal to use set_pxx_at() for ZONE_DEVICE pages for page
fault resolutions, skip all the checks if page_ext doesn't even exist in
pgtable checker, which applies to ZONE_DEVICE but maybe more.

 References:
https://git.kernel.org/stable/c/51897f99351fff7b57f4f141940fa93b4e90fd2b
https://git.kernel.org/stable/c/84d3549d54f5ff9fa3281257be3019386f51d1a0
https://git.kernel.org/stable/c/dec2382247860d2134c8d41e103e26460c099629
https://git.kernel.org/stable/c/8bb592c2eca8fd2bc06db7d80b38da18da4a2f43
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