[PATCH 3.12 126/170] mm: fix crashes from mbind() merging vmas

Jiri Slaby
2014-07-18T13:19:32Z

From: Hugh Dickins <hughd@google.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit d05f0cdcbe6388723f1900c549b4850360545201 upstream.

In v2.6.34 commit 9d8cebd4bcd7 ("mm: fix mbind vma merge problem")
introduced vma merging to mbind(), but it should have also changed the
convention of passing start vma from queue_pages_range() (formerly
check_range()) to new_vma_page(): vma merging may have already freed
that structure, resulting in BUG at mm/mempolicy.c:1738 and probably
worse crashes.

Fixes: 9d8cebd4bcd7 ("mm: fix mbind vma merge problem")
Reported-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
mm/mempolicy.c | 46 ++++++++++++++++++++--------------------------
1 file changed, 20 insertions(+), 26 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a005cc9f6f18..945316989352 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -653,19 +653,18 @@ static unsigned long change_prot_numa(struct vm_area_struct *vma,
* @nodes and @flags,) it's isolated and queued to the pagelist which is
* passed via @private.)
*/
-static struct vm_area_struct *
+static int
queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
const nodemask_t *nodes, unsigned long flags, void *private)
{
- int err;
- struct vm_area_struct *first, *vma, *prev;
-
+ int err = 0;
+ struct vm_area_struct *vma, *prev;

- first = find_vma(mm, start);
- if (!first)
- return ERR_PTR(-EFAULT);
+ vma = find_vma(mm, start);
+ if (!vma)
+ return -EFAULT;
prev = NULL;
- for (vma = first; vma && vma->vm_start < end; vma = vma->vm_next) {
+ for (; vma && vma->vm_start < end; vma = vma->vm_next) {
unsigned long endvma = vma->vm_end;

if (endvma > end)
@@ -675,9 +674,9 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,

if (!(flags & MPOL_MF_DISCONTIG_OK)) {
if (!vma->vm_next && vma->vm_end < end)
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
if (prev && prev->vm_end < vma->vm_start)
- return ERR_PTR(-EFAULT);
+ return -EFAULT;
}

if (flags & MPOL_MF_LAZY) {
@@ -691,15 +690,13 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,

err = queue_pages_pgd_range(vma, start, endvma, nodes,
flags, private);
- if (err) {
- first = ERR_PTR(err);
+ if (err)
break;
- }
}
next:
prev = vma;
}
- return first;
+ return err;
}

/*
@@ -1184,16 +1181,17 @@ out:

/*
* Allocate a new page for page migration based on vma policy.
- * Start assuming that page is mapped by vma pointed to by @private.
+ * Start by assuming the page is mapped by the same vma as contains @start.
* Search forward from there, if not. N.B., this assumes that the
* list of pages handed to migrate_pages()--which is how we get here--
* is in virtual address order.
*/
-static struct page *new_vma_page(struct page *page, unsigned long private, int **x)
+static struct page *new_page(struct page *page, unsigned long start, int **x)
{
- struct vm_area_struct *vma = (struct vm_area_struct *)private;
+ struct vm_area_struct *vma;
unsigned long uninitialized_var(address);

+ vma = find_vma(current->mm, start);
while (vma) {
address = page_address_in_vma(page, vma);
if (address != -EFAULT)
@@ -1223,7 +1221,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
return -ENOSYS;
}

-static struct page *new_vma_page(struct page *page, unsigned long private, int **x)
+static struct page *new_page(struct page *page, unsigned long start, int **x)
{
return NULL;
}
@@ -1233,7 +1231,6 @@ static long do_mbind(unsigned long start, unsigned long len,
unsigned short mode, unsigned short mode_flags,
nodemask_t *nmask, unsigned long flags)
{
- struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
struct mempolicy *new;
unsigned long end;
@@ -1299,11 +1296,9 @@ static long do_mbind(unsigned long start, unsigned long len,
if (err)
goto mpol_out;

- vma = queue_pages_range(mm, start, end, nmask,
+ err = queue_pages_range(mm, start, end, nmask,
flags | MPOL_MF_INVERT, &pagelist);
-
- err = PTR_ERR(vma); /* maybe ... */
- if (!IS_ERR(vma))
+ if (!err)
err = mbind_range(mm, start, end, new);

if (!err) {
@@ -1311,9 +1306,8 @@ static long do_mbind(unsigned long start, unsigned long len,

if (!list_empty(&pagelist)) {
WARN_ON_ONCE(flags & MPOL_MF_LAZY);
- nr_failed = migrate_pages(&pagelist, new_vma_page,
- (unsigned long)vma,
- MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
+ nr_failed = migrate_pages(&pagelist, new_page,
+ start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
if (nr_failed)
putback_movable_pages(&pagelist);
}
--
2.0.0