arch/x86_64: fix page table levels in pgalloc - #19692
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Two level errors corrupted kernel memory when a user process extended its heap with sbrk: - PGT_LAST was X86_MMU_PT_LEVELS (4), but valid levels are 0-3, so the final level entry was written with an out-of-range index. - x86_64_get_pgtable indexed the PD (level 2) with level 3, installing newly allocated page tables into the wrong PD slot. Signed-off-by: raiden00pl <raiden00@railab.me> Assisted-by: Claude Code
xiaoxiang781216
approved these changes
Aug 5, 2026
jerpelea
approved these changes
Aug 5, 2026
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Arch: x86_64
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Summary
Two level errors corrupted kernel memory when a user process extended its heap with sbrk:
PGT_LAST was X86_MMU_PT_LEVELS (4), but valid levels are 0-3, so the final level entry was written with an out-of-range index.
x86_64_get_pgtable indexed the PD (level 2) with level 3, installing newly allocated page tables into the wrong PD slot.
Impact
fix for kernel build
Testing
qemu-intel64 kernel build with ostest