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mm/pagewalk.c: walk_page_range should avoid VM_PFNMAP areas

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A panic can be caused by simply cat'ing /proc/<pid>/smaps while an
application has a VM_PFNMAP range.  It happened in-house when a
benchmarker was trying to decipher the memory layout of his program.

/proc/<pid>/smaps and similar walks through a user page table should not
be looking at VM_PFNMAP areas.

Certain tests in walk_page_range() (specifically split_huge_page_pmd())
assume that all the mapped PFN's are backed with page structures.  And
this is not usually true for VM_PFNMAP areas.  This can result in panics
on kernel page faults when attempting to address those page structures.

There are a half dozen callers of walk_page_range() that walk through a
task's entire page table (as N.  Horiguchi pointed out).  So rather than
change all of them, this patch changes just walk_page_range() to ignore
VM_PFNMAP areas.

The logic of hugetlb_vma() is moved back into walk_page_range(), as we
want to test any vma in the range.

VM_PFNMAP areas are used by:
- graphics memory manager   gpu/drm/drm_gem.c
- global reference unit     sgi-gru/grufile.c
- sgi special memory        char/mspec.c
- and probably several out-of-tree modules

[[email protected]: remove now-unused hugetlb_vma() stub]
Signed-off-by: Cliff Wickman <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Cliff Wickman 2013-05-24 15:55:36 -07:00 • committed by Linus Torvalds
commit a9ff785e44
1 changed files with 36 additions and 34 deletions
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72
mm/pagewalk.c
View file

@ -127,28 +127,7 @@ static int walk_hugetlb_range(struct vm_area_struct *vma,
return 0;
}
static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
{
struct vm_area_struct *vma;
/* We don't need vma lookup at all. */
if (!walk->hugetlb_entry)
return NULL;
VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
vma = find_vma(walk->mm, addr);
if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
return vma;
return NULL;
}
#else /* CONFIG_HUGETLB_PAGE */
static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
{
return NULL;
}
static int walk_hugetlb_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
@ -198,30 +177,53 @@ int walk_page_range(unsigned long addr, unsigned long end,
if (!walk->mm)
return -EINVAL;
VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
pgd = pgd_offset(walk->mm, addr);
do {
struct vm_area_struct *vma;
struct vm_area_struct *vma = NULL;
next = pgd_addr_end(addr, end);
/*
* handle hugetlb vma individually because pagetable walk for
* the hugetlb page is dependent on the architecture and
* we can't handled it in the same manner as non-huge pages.
* This function was not intended to be vma based.
* But there are vma special cases to be handled:
* - hugetlb vma's
* - VM_PFNMAP vma's
*/
vma = hugetlb_vma(addr, walk);
vma = find_vma(walk->mm, addr);
if (vma) {
if (vma->vm_end < next)
next = vma->vm_end;
/*
* Hugepage is very tightly coupled with vma, so
* walk through hugetlb entries within a given vma.
* There are no page structures backing a VM_PFNMAP
* range, so do not allow split_huge_page_pmd().
*/
err = walk_hugetlb_range(vma, addr, next, walk);
if (err)
break;
pgd = pgd_offset(walk->mm, next);
continue;
if ((vma->vm_start <= addr) &&
(vma->vm_flags & VM_PFNMAP)) {
next = vma->vm_end;
pgd = pgd_offset(walk->mm, next);
continue;
}
/*
* Handle hugetlb vma individually because pagetable
* walk for the hugetlb page is dependent on the
* architecture and we can't handled it in the same
* manner as non-huge pages.
*/
if (walk->hugetlb_entry && (vma->vm_start <= addr) &&
is_vm_hugetlb_page(vma)) {
if (vma->vm_end < next)
next = vma->vm_end;
/*
* Hugepage is very tightly coupled with vma,
* so walk through hugetlb entries within a
* given vma.
*/
err = walk_hugetlb_range(vma, addr, next, walk);
if (err)
break;
pgd = pgd_offset(walk->mm, next);
continue;
}
}
if (pgd_none_or_clear_bad(pgd)) {