Messages in this thread | | | Date | Sat, 18 Jun 2022 03:22:20 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH] x86/mm: Fix possible index overflow when creating page table mapping |
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On Thu, Jun 16, 2022 at 09:55:10PM +0800, Yuntao Wang wrote: > There are two issues in phys_p4d_init(): > > - The __kernel_physical_mapping_init() does not do boundary-checking for > paddr_end and passes it directly to phys_p4d_init(), phys_p4d_init() does > not do bounds checking either, so if the physical memory to be mapped is > large enough, 'p4d_page + p4d_index(vaddr)' will wrap around to the > beginning entry of the P4D table and its data will be overwritten. > > - The for loop body will be executed only when 'vaddr < vaddr_end' > evaluates to true, but if that condition is true, 'paddr >= paddr_end' > will evaluate to false, thus the 'if (paddr >= paddr_end) {}' block will > never be executed and become dead code. > > To fix these issues, use 'i < PTRS_PER_P4D' instead of 'vaddr < vaddr_end' > as the for loop condition, this also make it more consistent with the logic > of the phys_{pud,pmt,pte}_init() functions.
Hm. I don't see why you changed phys_p4d_init(), but not __kernel_physical_mapping_init(). It does exactly the same thing, just pgd_index() is hidden a bit deeper than p4d_index().
-- Kirill A. Shutemov
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