The patch titled
Subject: mm/mmap.c: replace find_vma_prepare() with clearer find_vma_links()
has been added to the -mm tree. Its filename is
mm-mmapc-replace-find_vma_prepare-with-clearer-find_vma_links.patch
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From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: 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.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Benny Halevy <bhalevy@xxxxxxxxxx>
Acked-by: Hillf Danton <dhillf@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 45 +++++++++++++++++++++------------------------
1 file changed, 21 insertions(+), 24 deletions(-)
diff -puN mm/mmap.c~mm-mmapc-replace-find_vma_prepare-with-clearer-find_vma_links mm/mmap.c
--- a/mm/mmap.c~mm-mmapc-replace-find_vma_prepare-with-clearer-find_vma_links
+++ a/mm/mmap.c
@@ -353,17 +353,14 @@ void validate_mm(struct mm_struct *mm)
#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 @@ find_vma_prepare(struct mm_struct *mm, u
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 @@ find_vma_prepare(struct mm_struct *mm, u
*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 vma_link(struct mm_struct *m
*/
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 @@ unsigned long mmap_region(struct file *f
/* 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;
@@ -2185,8 +2182,7 @@ static unsigned long do_brk(unsigned lon
* 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;
@@ -2300,10 +2296,10 @@ void exit_mmap(struct mm_struct *mm)
* 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
@@ -2321,8 +2317,8 @@ int insert_vm_struct(struct mm_struct *
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)))
@@ -2356,7 +2352,8 @@ struct vm_area_struct *copy_vma(struct v
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))
+ BUG();
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) {
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-change-nr_ptes-bug_on-to-warn_on.patch
x86-pat-remove-the-dependency-on-vm_pgoff-in-track-untrack-pfn-vma-routines.patch
x86-pat-separate-the-pfn-attribute-tracking-for-remap_pfn_range-and-vm_insert_pfn.patch
mm-x86-pat-rework-linear-pfn-mmap-tracking.patch
mm-introduce-arch-specific-vma-flag-vm_arch_1.patch
mm-kill-vma-flag-vm_insertpage.patch
mm-kill-vma-flag-vm_can_nonlinear.patch
mm-use-mm-exe_file-instead-of-first-vm_executable-vma-vm_file.patch
mm-kill-vma-flag-vm_executable-and-mm-num_exe_file_vmas.patch
mm-prepare-vm_dontdump-for-using-in-drivers.patch
mm-kill-vma-flag-vm_reserved-and-mm-reserved_vm-counter.patch
mm-mmapc-replace-find_vma_prepare-with-clearer-find_vma_links.patch
prio_tree-debugging-patch.patch
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