From: Lai Jiangshan <[email protected]> The commit 825d0b73cd752("x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()") handles unaligned address well for unmapped PUD/PMD etc. But unaligned address for mapped pmd also needs to be aware.
For mapped pmd, if @addr is not aligned to PMD_SIZE, the next pmd (PTI_CLONE_PMD or the next pmd is large) or the last ptes (PTI_CLONE_PTE) in the next pmd will not be cloned when @end < @addr + PMD_SIZE in the current logic in the code. It is not a good idea to force alignment in the caller due to one of the cases (see the comments in the code), so it just handles the alignment in pti_clone_pagetable(). Signed-off-by: Lai Jiangshan <[email protected]> --- arch/x86/mm/pti.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 1aab92930569..7ee99ef13a99 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -342,6 +342,21 @@ pti_clone_pgtable(unsigned long start, unsigned long end, } if (pmd_large(*pmd) || level == PTI_CLONE_PMD) { + /* + * pti_clone_kernel_text() might be called with + * @start not aligned to PMD_SIZE. We need to make + * it aligned, otherwise the next pmd or last ptes + * are not cloned when @end < @addr + PMD_SIZE. + * + * We can't force pti_clone_kernel_text() to align + * the @addr to PMD_SIZE when level == PTI_CLONE_PTE. + * But the problem can still possible exist when the + * first pmd is large. And it is not a good idea to + * check whether the first pmd is large or not in the + * caller, so we just simply align it here. + */ + addr = round_down(addr, PMD_SIZE); + target_pmd = pti_user_pagetable_walk_pmd(addr); if (WARN_ON(!target_pmd)) return; -- 2.19.1.6.gb485710b
