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Subject[ 49/72] NOMMU: Lock i_mmap_mutex for access to the VMA prio list
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
From: David Howells <dhowells@redhat.com>

commit 918e556ec214ed2f584e4cac56d7b29e4bb6bf27 upstream.

Lock i_mmap_mutex for access to the VMA prio list to prevent concurrent
access. Currently, certain parts of the mmap handling are protected by
the region mutex, but not all.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/nommu.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -696,9 +696,11 @@ static void add_vma_to_mm(struct mm_stru
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;

+ mutex_lock(&mapping->i_mmap_mutex);
flush_dcache_mmap_lock(mapping);
vma_prio_tree_insert(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
+ mutex_unlock(&mapping->i_mmap_mutex);
}

/* add the VMA to the tree */
@@ -760,9 +762,11 @@ static void delete_vma_from_mm(struct vm
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;

+ mutex_lock(&mapping->i_mmap_mutex);
flush_dcache_mmap_lock(mapping);
vma_prio_tree_remove(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
+ mutex_unlock(&mapping->i_mmap_mutex);
}

/* remove from the MM's tree and list */
@@ -2052,6 +2056,7 @@ int nommu_shrink_inode_mappings(struct i
high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

down_write(&nommu_region_sem);
+ mutex_lock(&inode->i_mapping->i_mmap_mutex);

/* search for VMAs that fall within the dead zone */
vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
@@ -2059,6 +2064,7 @@ int nommu_shrink_inode_mappings(struct i
/* found one - only interested if it's shared out of the page
* cache */
if (vma->vm_flags & VM_SHARED) {
+ mutex_unlock(&inode->i_mapping->i_mmap_mutex);
up_write(&nommu_region_sem);
return -ETXTBSY; /* not quite true, but near enough */
}
@@ -2086,6 +2092,7 @@ int nommu_shrink_inode_mappings(struct i
}
}

+ mutex_unlock(&inode->i_mapping->i_mmap_mutex);
up_write(&nommu_region_sem);
return 0;
}



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