Re: [PATCH 3.2 099/125] mm: fix crashes from mbind() merging vmas

Hugh Dickins
2014-07-08T20:47:33Z

On Tue, 8 Jul 2014, Ben Hutchings wrote:

> 3.2.61-rc1 review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Hugh Dickins <hughd@google.com>
>
> 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>
> [bwh: Backported to 3.2:
> - Adjust context
> - Keep the same arguments to migrate_pages() except for private=start]
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
> mm/mempolicy.c | 46 ++++++++++++++++++++--------------------------
> 1 file changed, 20 insertions(+), 26 deletions(-)
>
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -566,24 +566,23 @@ static inline int check_pgd_range(struct
> * If pagelist != NULL then isolate pages from the LRU and
> * put them on the pagelist.
> */
> -static struct vm_area_struct *
> +static int
> check_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) {
> 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 (!is_vm_hugetlb_page(vma) &&
> ((flags & MPOL_MF_STRICT) ||
> @@ -597,14 +596,12 @@ check_range(struct mm_struct *mm, unsign
> start = vma->vm_start;
> err = check_pgd_range(vma, start, endvma, nodes,
> flags, private);
> - if (err) {
> - first = ERR_PTR(err);
> + if (err)
> break;
> - }
> }
> prev = vma;
> }
> - return first;
> + return err;
> }
>
> /*
> @@ -1060,16 +1057,17 @@ 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)
> @@ -1095,7 +1093,7 @@ int do_migrate_pages(struct mm_struct *m
> 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;
> }
> @@ -1105,7 +1103,6 @@ static long do_mbind(unsigned long start
> 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;
> @@ -1169,19 +1166,16 @@ static long do_mbind(unsigned long start
> if (err)
> goto mpol_out;
>
> - vma = check_range(mm, start, end, nmask,
> + err = check_range(mm, start, end, nmask,
> flags | MPOL_MF_INVERT, &pagelist);
> -
> - err = PTR_ERR(vma);
> - if (!IS_ERR(vma)) {
> + if (!err) {
> int nr_failed = 0;
>
> err = mbind_range(mm, start, end, new);
>
> if (!list_empty(&pagelist)) {
> - nr_failed = migrate_pages(&pagelist, new_vma_page,
> - (unsigned long)vma,
> - false, true);
> + nr_failed = migrate_pages(&pagelist, new_page,
> + start, false, true);
> if (nr_failed)
> putback_lru_pages(&pagelist);
> }

I don't think that's correct, I can't see a change to the
"vma = check_range(" in migrate_to_node() which 3.2 and 3.4 trees have.
Does it build (without warning) with CONFIG_NUMA and CONFIG_MIGRATION?
I expect this version I sent yesterday for 3.4.98 will be good for 3.2:

------------------ version for 3.4.98 ------------------

>From d05f0cdcbe6388723f1900c549b4850360545201 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Mon, 23 Jun 2014 13:22:07 -0700
Subject: [PATCH] mm: fix crashes from mbind() merging vmas

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>
Cc: <stable@vger.kernel.org> [2.6.34+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -566,24 +566,24 @@ static inline int check_pgd_range(struct
* If pagelist != NULL then isolate pages from the LRU and
* put them on the pagelist.
*/
-static struct vm_area_struct *
+static int
check_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) {
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 (!is_vm_hugetlb_page(vma) &&
((flags & MPOL_MF_STRICT) ||
@@ -597,14 +597,12 @@ check_range(struct mm_struct *mm, unsign
start = vma->vm_start;
err = check_pgd_range(vma, start, endvma, nodes,
flags, private);
- if (err) {
- first = ERR_PTR(err);
+ if (err)
break;
- }
}
prev = vma;
}
- return first;
+ return err;
}

/*
@@ -945,16 +943,15 @@ static int migrate_to_node(struct mm_str
{
nodemask_t nmask;
LIST_HEAD(pagelist);
- int err = 0;
- struct vm_area_struct *vma;
+ int err;

nodes_clear(nmask);
node_set(source, nmask);

- vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
+ err = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
flags | MPOL_MF_DISCONTIG_OK, &pagelist);
- if (IS_ERR(vma))
- return PTR_ERR(vma);
+ if (err)
+ return err;

if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, new_node_page, dest,
@@ -1058,16 +1055,17 @@ 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)
@@ -1093,7 +1091,7 @@ int do_migrate_pages(struct mm_struct *m
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;
}
@@ -1103,7 +1101,6 @@ static long do_mbind(unsigned long start
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;
@@ -1167,19 +1164,17 @@ static long do_mbind(unsigned long start
if (err)
goto mpol_out;

- vma = check_range(mm, start, end, nmask,
+ err = check_range(mm, start, end, nmask,
flags | MPOL_MF_INVERT, &pagelist);

- err = PTR_ERR(vma);
- if (!IS_ERR(vma)) {
+ if (!err) {
int nr_failed = 0;

err = mbind_range(mm, start, end, new);

if (!list_empty(&pagelist)) {
- nr_failed = migrate_pages(&pagelist, new_vma_page,
- (unsigned long)vma,
- false, true);
+ nr_failed = migrate_pages(&pagelist, new_page,
+ start, false, true);
if (nr_failed)
putback_lru_pages(&pagelist);
}