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Merge branch 'vm' of git://git.kernel.org/pub/scm/linux/kernel/git/vi…
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…ro/vfs

Pull munmap/truncate race fixes from Al Viro:
 "Fixes for racy use of unmap_vmas() on truncate-related codepaths"

* 'vm' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  VM: make zap_page_range() callers that act on a single VMA use separate helper
  VM: make unmap_vmas() return void
  VM: don't bother with feeding upper limit to tlb_finish_mmu() in exit_mmap()
  VM: make zap_page_range() return void
  VM: can't go through the inner loop in unmap_vmas() more than once...
  VM: unmap_page_range() can return void
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@torvalds
torvalds committed Mar 21, 2012
2 parents 3556485 + f5cc4ee commit 3a990a5
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Showing 3 changed files with 84 additions and 58 deletions.
4 changes: 2 additions & 2 deletions include/linux/mm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -893,9 +893,9 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,

int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
void zap_page_range(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *);
unsigned long unmap_vmas(struct mmu_gather *tlb,
void unmap_vmas(struct mmu_gather *tlb,
struct vm_area_struct *start_vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *);
Expand Down
133 changes: 80 additions & 53 deletions mm/memory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1282,10 +1282,10 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
return addr;
}

static unsigned long unmap_page_range(struct mmu_gather *tlb,
struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct zap_details *details)
static void unmap_page_range(struct mmu_gather *tlb,
struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
pgd_t *pgd;
unsigned long next;
Expand All @@ -1305,8 +1305,47 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb,
} while (pgd++, addr = next, addr != end);
tlb_end_vma(tlb, vma);
mem_cgroup_uncharge_end();
}

return addr;

static void unmap_single_vma(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *details)
{
unsigned long start = max(vma->vm_start, start_addr);
unsigned long end;

if (start >= vma->vm_end)
return;
end = min(vma->vm_end, end_addr);
if (end <= vma->vm_start)
return;

if (vma->vm_flags & VM_ACCOUNT)
*nr_accounted += (end - start) >> PAGE_SHIFT;

if (unlikely(is_pfn_mapping(vma)))
untrack_pfn_vma(vma, 0, 0);

if (start != end) {
if (unlikely(is_vm_hugetlb_page(vma))) {
/*
* It is undesirable to test vma->vm_file as it
* should be non-null for valid hugetlb area.
* However, vm_file will be NULL in the error
* cleanup path of do_mmap_pgoff. When
* hugetlbfs ->mmap method fails,
* do_mmap_pgoff() nullifies vma->vm_file
* before calling this function to clean up.
* Since no pte has actually been setup, it is
* safe to do nothing in this case.
*/
if (vma->vm_file)
unmap_hugepage_range(vma, start, end, NULL);
} else
unmap_page_range(tlb, vma, start, end, details);
}
}

/**
Expand All @@ -1318,8 +1357,6 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb,
* @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
* @details: details of nonlinear truncation or shared cache invalidation
*
* Returns the end address of the unmapping (restart addr if interrupted).
*
* Unmap all pages in the vma list.
*
* Only addresses between `start' and `end' will be unmapped.
Expand All @@ -1331,55 +1368,18 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb,
* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
* drops the lock and schedules.
*/
unsigned long unmap_vmas(struct mmu_gather *tlb,
void unmap_vmas(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *details)
{
unsigned long start = start_addr;
struct mm_struct *mm = vma->vm_mm;

mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
unsigned long end;

start = max(vma->vm_start, start_addr);
if (start >= vma->vm_end)
continue;
end = min(vma->vm_end, end_addr);
if (end <= vma->vm_start)
continue;

if (vma->vm_flags & VM_ACCOUNT)
*nr_accounted += (end - start) >> PAGE_SHIFT;

if (unlikely(is_pfn_mapping(vma)))
untrack_pfn_vma(vma, 0, 0);

while (start != end) {
if (unlikely(is_vm_hugetlb_page(vma))) {
/*
* It is undesirable to test vma->vm_file as it
* should be non-null for valid hugetlb area.
* However, vm_file will be NULL in the error
* cleanup path of do_mmap_pgoff. When
* hugetlbfs ->mmap method fails,
* do_mmap_pgoff() nullifies vma->vm_file
* before calling this function to clean up.
* Since no pte has actually been setup, it is
* safe to do nothing in this case.
*/
if (vma->vm_file)
unmap_hugepage_range(vma, start, end, NULL);

start = end;
} else
start = unmap_page_range(tlb, vma, start, end, details);
}
}

for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
unmap_single_vma(tlb, vma, start_addr, end_addr, nr_accounted,
details);
mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
return start; /* which is now the end (or restart) address */
}

/**
Expand All @@ -1388,8 +1388,34 @@ unsigned long unmap_vmas(struct mmu_gather *tlb,
* @address: starting address of pages to zap
* @size: number of bytes to zap
* @details: details of nonlinear truncation or shared cache invalidation
*
* Caller must protect the VMA list
*/
void zap_page_range(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *details)
{
struct mm_struct *mm = vma->vm_mm;
struct mmu_gather tlb;
unsigned long end = address + size;
unsigned long nr_accounted = 0;

lru_add_drain();
tlb_gather_mmu(&tlb, mm, 0);
update_hiwater_rss(mm);
unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
tlb_finish_mmu(&tlb, address, end);
}

/**
* zap_page_range_single - remove user pages in a given range
* @vma: vm_area_struct holding the applicable pages
* @address: starting address of pages to zap
* @size: number of bytes to zap
* @details: details of nonlinear truncation or shared cache invalidation
*
* The range must fit into one VMA.
*/
unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *details)
{
struct mm_struct *mm = vma->vm_mm;
Expand All @@ -1400,9 +1426,10 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
lru_add_drain();
tlb_gather_mmu(&tlb, mm, 0);
update_hiwater_rss(mm);
end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
mmu_notifier_invalidate_range_start(mm, address, end);
unmap_single_vma(&tlb, vma, address, end, &nr_accounted, details);
mmu_notifier_invalidate_range_end(mm, address, end);
tlb_finish_mmu(&tlb, address, end);
return end;
}

/**
Expand All @@ -1423,7 +1450,7 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
if (address < vma->vm_start || address + size > vma->vm_end ||
!(vma->vm_flags & VM_PFNMAP))
return -1;
zap_page_range(vma, address, size, NULL);
zap_page_range_single(vma, address, size, NULL);
return 0;
}
EXPORT_SYMBOL_GPL(zap_vma_ptes);
Expand Down Expand Up @@ -2770,7 +2797,7 @@ static void unmap_mapping_range_vma(struct vm_area_struct *vma,
unsigned long start_addr, unsigned long end_addr,
struct zap_details *details)
{
zap_page_range(vma, start_addr, end_addr - start_addr, details);
zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
}

static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
Expand Down
5 changes: 2 additions & 3 deletions mm/mmap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2237,7 +2237,6 @@ void exit_mmap(struct mm_struct *mm)
struct mmu_gather tlb;
struct vm_area_struct *vma;
unsigned long nr_accounted = 0;
unsigned long end;

/* mm's last user has gone, and its about to be pulled down */
mmu_notifier_release(mm);
Expand All @@ -2262,11 +2261,11 @@ void exit_mmap(struct mm_struct *mm)
tlb_gather_mmu(&tlb, mm, 1);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use -1 here to ensure all VMAs in the mm are unmapped */
end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
vm_unacct_memory(nr_accounted);

free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
tlb_finish_mmu(&tlb, 0, end);
tlb_finish_mmu(&tlb, 0, -1);

/*
* Walk the list again, actually closing and freeing it,
Expand Down

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