mm/mmap.c: replace find_vma_prepare() with clearer find_vma_links()
People get confused by find_vma_prepare(), because it doesn't care about
what it returns in its output args, when its callers won't be interested.
Clarify by passing in end-of-range address too, and returning failure if
any existing vma overlaps the new range: instead of returning an ambiguous
vma which most callers then must check. find_vma_links() is a clearer
name.
This does revert 2.6.27's dfe195fb79e88 ("mm: fix uninitialized variables
for find_vma_prepare callers"), but it looks like gcc 4.3.0 was one of
those releases too eager to shout about uninitialized variables: only
copy_vma() warns with 4.5.1 and 4.7.1, which a BUG on error silences.
[hughd@google.com: fix warning, remove BUG()]
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Benny Halevy <bhalevy@tonian.com>
Acked-by: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index a76042d..2ba2743 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -353,17 +353,14 @@
#define validate_mm(mm) do { } while (0)
#endif
-static struct vm_area_struct *
-find_vma_prepare(struct mm_struct *mm, unsigned long addr,
- struct vm_area_struct **pprev, struct rb_node ***rb_link,
- struct rb_node ** rb_parent)
+static int find_vma_links(struct mm_struct *mm, unsigned long addr,
+ unsigned long end, struct vm_area_struct **pprev,
+ struct rb_node ***rb_link, struct rb_node **rb_parent)
{
- struct vm_area_struct * vma;
- struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
+ struct rb_node **__rb_link, *__rb_parent, *rb_prev;
__rb_link = &mm->mm_rb.rb_node;
rb_prev = __rb_parent = NULL;
- vma = NULL;
while (*__rb_link) {
struct vm_area_struct *vma_tmp;
@@ -372,9 +369,9 @@
vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
if (vma_tmp->vm_end > addr) {
- vma = vma_tmp;
- if (vma_tmp->vm_start <= addr)
- break;
+ /* Fail if an existing vma overlaps the area */
+ if (vma_tmp->vm_start < end)
+ return -ENOMEM;
__rb_link = &__rb_parent->rb_left;
} else {
rb_prev = __rb_parent;
@@ -387,7 +384,7 @@
*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
*rb_link = __rb_link;
*rb_parent = __rb_parent;
- return vma;
+ return 0;
}
void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -456,11 +453,12 @@
*/
static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
- struct vm_area_struct *__vma, *prev;
+ struct vm_area_struct *prev;
struct rb_node **rb_link, *rb_parent;
- __vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
- BUG_ON(__vma && __vma->vm_start < vma->vm_end);
+ if (find_vma_links(mm, vma->vm_start, vma->vm_end,
+ &prev, &rb_link, &rb_parent))
+ BUG();
__vma_link(mm, vma, prev, rb_link, rb_parent);
mm->map_count++;
}
@@ -1221,8 +1219,7 @@
/* Clear old maps */
error = -ENOMEM;
munmap_back:
- vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
- if (vma && vma->vm_start < addr + len) {
+ if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
if (do_munmap(mm, addr, len))
return -ENOMEM;
goto munmap_back;
@@ -2183,8 +2180,7 @@
* Clear old maps. this also does some error checking for us
*/
munmap_back:
- vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
- if (vma && vma->vm_start < addr + len) {
+ if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
if (do_munmap(mm, addr, len))
return -ENOMEM;
goto munmap_back;
@@ -2298,10 +2294,10 @@
* and into the inode's i_mmap tree. If vm_file is non-NULL
* then i_mmap_mutex is taken here.
*/
-int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
+int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
- struct vm_area_struct * __vma, * prev;
- struct rb_node ** rb_link, * rb_parent;
+ struct vm_area_struct *prev;
+ struct rb_node **rb_link, *rb_parent;
/*
* The vm_pgoff of a purely anonymous vma should be irrelevant
@@ -2319,8 +2315,8 @@
BUG_ON(vma->anon_vma);
vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
}
- __vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
- if (__vma && __vma->vm_start < vma->vm_end)
+ if (find_vma_links(mm, vma->vm_start, vma->vm_end,
+ &prev, &rb_link, &rb_parent))
return -ENOMEM;
if ((vma->vm_flags & VM_ACCOUNT) &&
security_vm_enough_memory_mm(mm, vma_pages(vma)))
@@ -2354,7 +2350,8 @@
faulted_in_anon_vma = false;
}
- find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
+ if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
+ return NULL; /* should never get here */
new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
if (new_vma) {