Commit 705e87c0 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

[PATCH] mm: pte_offset_map_lock loops 



Convert those common loops using page_table_lock on the outside and
pte_offset_map within to use just pte_offset_map_lock within instead.

These all hold mmap_sem (some exclusively, some not), so at no level can a
page table be whipped away from beneath them.  But whereas pte_alloc loops
tested with the "atomic" pmd_present, these loops are testing with pmd_none,
which on i386 PAE tests both lower and upper halves.

That's now unsafe, so add a cast into pmd_none to test only the vital lower
half: we lose a little sensitivity to a corrupt middle directory, but not
enough to worry about.  It appears that i386 and UML were the only
architectures vulnerable in this way, and pgd and pud no problem.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8f4e2101

fs/proc/task_mmu.c

+6 −11
Original line number Diff line number Diff line
@@ -203,13 +203,14 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 
				struct mem_size_stats *mss)

{

	pte_t *pte, ptent;

	spinlock_t *ptl;

	unsigned long pfn;

	struct page *page;



	pte = pte_offset_map(pmd, addr);

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	do {

		ptent = *pte;

		if (pte_none(ptent) || !pte_present(ptent))

		if (!pte_present(ptent))

			continue;



		mss->resident += PAGE_SIZE;
@@ -230,8 +231,8 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 
				mss->private_clean += PAGE_SIZE;

		}

	} while (pte++, addr += PAGE_SIZE, addr != end);

	pte_unmap(pte - 1);

	cond_resched_lock(&vma->vm_mm->page_table_lock);

	pte_unmap_unlock(pte - 1, ptl);

	cond_resched();

}



static inline void smaps_pmd_range(struct vm_area_struct *vma, pud_t *pud,
@@ -285,17 +286,11 @@ static inline void smaps_pgd_range(struct vm_area_struct *vma, 
static int show_smap(struct seq_file *m, void *v)

{

	struct vm_area_struct *vma = v;

	struct mm_struct *mm = vma->vm_mm;

	struct mem_size_stats mss;



	memset(&mss, 0, sizeof mss);



	if (mm) {

		spin_lock(&mm->page_table_lock);

	if (vma->vm_mm)

		smaps_pgd_range(vma, vma->vm_start, vma->vm_end, &mss);

		spin_unlock(&mm->page_table_lock);

	}



	return show_map_internal(m, v, &mss);

}

include/asm-i386/pgtable.h

+2 −1
Original line number Diff line number Diff line
@@ -203,7 +203,8 @@ extern unsigned long pg0[]; 
#define pte_present(x)	((x).pte_low & (_PAGE_PRESENT | _PAGE_PROTNONE))

#define pte_clear(mm,addr,xp)	do { set_pte_at(mm, addr, xp, __pte(0)); } while (0)



#define pmd_none(x)	(!pmd_val(x))

/* To avoid harmful races, pmd_none(x) should check only the lower when PAE */

#define pmd_none(x)	(!(unsigned long)pmd_val(x))

#define pmd_present(x)	(pmd_val(x) & _PAGE_PRESENT)

#define pmd_clear(xp)	do { set_pmd(xp, __pmd(0)); } while (0)

#define	pmd_bad(x)	((pmd_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)

include/asm-um/pgtable.h

+1 −1
Original line number Diff line number Diff line
@@ -138,7 +138,7 @@ extern unsigned long pg0[1024]; 


#define pte_clear(mm,addr,xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEWPAGE))



#define pmd_none(x)	(!(pmd_val(x) & ~_PAGE_NEWPAGE))

#define pmd_none(x)	(!((unsigned long)pmd_val(x) & ~_PAGE_NEWPAGE))

#define	pmd_bad(x)	((pmd_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)

#define pmd_present(x)	(pmd_val(x) & _PAGE_PRESENT)

#define pmd_clear(xp)	do { pmd_val(*(xp)) = _PAGE_NEWPAGE; } while (0)

mm/mempolicy.c

+3 −4
Original line number Diff line number Diff line
@@ -228,9 +228,9 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 
{

	pte_t *orig_pte;

	pte_t *pte;

	spinlock_t *ptl;



	spin_lock(&vma->vm_mm->page_table_lock);

	orig_pte = pte = pte_offset_map(pmd, addr);

	orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	do {

		unsigned long pfn;

		unsigned int nid;
@@ -246,8 +246,7 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 
		if (!node_isset(nid, *nodes))

			break;

	} while (pte++, addr += PAGE_SIZE, addr != end);

	pte_unmap(orig_pte);

	spin_unlock(&vma->vm_mm->page_table_lock);

	pte_unmap_unlock(orig_pte, ptl);

	return addr != end;

}

mm/mprotect.c

+3 −4
Original line number Diff line number Diff line
@@ -29,8 +29,9 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, 
		unsigned long addr, unsigned long end, pgprot_t newprot)

{

	pte_t *pte;

	spinlock_t *ptl;



	pte = pte_offset_map(pmd, addr);

	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);

	do {

		if (pte_present(*pte)) {

			pte_t ptent;
@@ -44,7 +45,7 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, 
			lazy_mmu_prot_update(ptent);

		}

	} while (pte++, addr += PAGE_SIZE, addr != end);

	pte_unmap(pte - 1);

	pte_unmap_unlock(pte - 1, ptl);

}



static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
@@ -88,7 +89,6 @@ static void change_protection(struct vm_area_struct *vma, 
	BUG_ON(addr >= end);

	pgd = pgd_offset(mm, addr);

	flush_cache_range(vma, addr, end);

	spin_lock(&mm->page_table_lock);

	do {

		next = pgd_addr_end(addr, end);

		if (pgd_none_or_clear_bad(pgd))
@@ -96,7 +96,6 @@ static void change_protection(struct vm_area_struct *vma, 
		change_pud_range(mm, pgd, addr, next, newprot);

	} while (pgd++, addr = next, addr != end);

	flush_tlb_range(vma, start, end);

	spin_unlock(&mm->page_table_lock);

}



static int

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