CVE-2024-57945: riscv: mm: Fix the out of bound issue of vmemmap address
Description
In the Linux kernel, the following vulnerability has been resolved:
riscv: mm: Fix the out of bound issue of vmemmap address
In sparse vmemmap model, the virtual address of vmemmap is calculated as:
((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)).
And the struct page's va can be calculated with an offset:
(vmemmap + (pfn)).
However, when initializing struct pages, kernel actually starts from the
first page from the same section that phys_ram_base belongs to. If the
first page's physical address is not (phys_ram_base >> PAGE_SHIFT), then
we get an va below VMEMMAP_START when calculating va for it's struct page.
For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
first page in the same section is actually pfn 0x80000. During
init_unavailable_range(), we will initialize struct page for pfn 0x80000
with virtual address ((struct page *)VMEMMAP_START - 0x2000), which is
below VMEMMAP_START as well as PCI_IO_END.
This commit fixes this bug by introducing a new variable
'vmemmap_start_pfn' which is aligned with memory section size and using
it to calculate vmemmap address instead of phys_ram_base.
Classification
CVE ID: CVE-2024-57945
Affected Products
Vendor: Linux
Product: Linux
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.05% (probability of being exploited)
EPSS Percentile: 17.98% (scored less or equal to compared to others)
EPSS Date: 2025-02-19 (when was this score calculated)
References
https://git.kernel.org/stable/c/a4a7ac3d266008018f05fae53060fcb331151a14https://git.kernel.org/stable/c/d2bd51954ac8377c2f1eb1813e694788998add66
https://git.kernel.org/stable/c/f754f27e98f88428aaf6be6e00f5cbce97f62d4b