ARM: make_coherent: fix problems with highpte, part 1 (56dd4709) · Commits · 戴 / test

update_mmu_cache() is called with a page table already mapped. We call make_coherent(), which then calls adjust_pte() which wants to map other page tables. This causes kmap_atomic() to BUG() because the slot its trying to use is already taken. Since do_adjust_pte() modifies the page tables, we are also missing any form of locking, so we're risking corrupting the page tables. Fix this by using pte_offset_map_nested(), and taking the pte page table lock around do_adjust_pte(). Signed-off-by:

Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/fault-armv.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -67,6 +67,7 @@ static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address,

		static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
		{
		spinlock_t *ptl;
		pgd_t *pgd;
		pmd_t *pmd;
		pte_t *pte;
		@@ -80,11 +81,19 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
		if (pmd_none_or_clear_bad(pmd))
		return 0;

		pte = pte_offset_map(pmd, address);
		/*
		* This is called while another page table is mapped, so we
		* must use the nested version. This also means we need to
		* open-code the spin-locking.
		*/
		ptl = pte_lockptr(vma->vm_mm, pmd);
		pte = pte_offset_map_nested(pmd, address);
		spin_lock(ptl);

		ret = do_adjust_pte(vma, address, pte);

		pte_unmap(pte);
		spin_unlock(ptl);
		pte_unmap_nested(pte);

		return ret;
		}

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