Commit 6597d783 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

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 dfe195fb ("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: default avatarHugh Dickins <hughd@google.com>
Cc: Benny Halevy <bhalevy@tonian.com>
Acked-by: default avatarHillf Danton <dhillf@gmail.com>
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d741c9cd

mm/mmap.c

+21 −24
Original line number Diff line number Diff line
@@ -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;



	__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, unsigned long addr, 
		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, unsigned long addr, 
		*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 *mm, struct vm_area_struct *vma, 
 */

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 *file, unsigned long addr, 
	/* 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 @@ static unsigned long do_brk(unsigned long addr, unsigned long len) 
	 * 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;
@@ -2300,7 +2296,7 @@ void exit_mmap(struct mm_struct *mm) 
 */

int 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;



	/*
@@ -2319,8 +2315,8 @@ int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma) 
		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 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, 
		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) {

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