On Fri, 20 Jun 2014, Naoya Horiguchi wrote:
> On Fri, Jun 20, 2014 at 09:24:36AM -0500, Christoph Lameter wrote:
> > On Thu, 19 Jun 2014, Naoya Horiguchi wrote:
> >
> > > I'm suspecting that mbind_range() do something wrong around vma handling,
> > > but I don't have enough luck yet. Anyone has an idea?
> >
> > Well memory policy data corrupted. This looks like you were trying to do
> > page migration via mbind()?
>
> Right.
>
> > Could we get some more details as to what is
> > going on here? Specifically the parameters passed to mbind would be
> > interesting.
>
> My view about the kernel behavior was in another email a few hours ago.
> And as for what userspace did, I attach the reproducer below. It's simply
> doing mbind(mode=MPOL_BIND, flags=MPOL_MF_MOVE_ALL) on random
> address/length/node.
Thanks for the additional information earlier. ext4, so no shmem
shared mempolicy involved: that cuts down the bugspace considerably.
I agree from what you said that it looked like corrupt vm_area_struct
and hence corrupt policy.
Here's an obvious patch to try, entirely untested - thanks for the
reproducer, but I'd rather leave the testing to you. Sounds like
you have a useful fuzzer there: good catch.
[PATCH] mm: fix crashes from mbind() merging vmas
v2.6.34's 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 <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Cc: [email protected] # 2.6.34+
---
mm/mempolicy.c | 46 ++++++++++++++++++++--------------------------
1 file changed, 20 insertions(+), 26 deletions(-)
--- 3.16-rc1/mm/mempolicy.c 2014-06-16 00:28:55.116076530 -0700
+++ linux/mm/mempolicy.c 2014-06-20 12:40:00.000204558 -0700
@@ -656,19 +656,18 @@ static unsigned long change_prot_numa(st
* @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)
@@ -678,9 +677,9 @@ queue_pages_range(struct mm_struct *mm,
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) {
@@ -694,15 +693,13 @@ queue_pages_range(struct mm_struct *mm,
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;
}
/*
@@ -1156,16 +1153,17 @@ 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)
@@ -1195,7 +1193,7 @@ 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;
}
@@ -1205,7 +1203,6 @@ 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;
@@ -1271,11 +1268,9 @@ static long do_mbind(unsigned long start
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) {
@@ -1283,9 +1278,8 @@ static long do_mbind(unsigned long start
if (!list_empty(&pagelist)) {
WARN_ON_ONCE(flags & MPOL_MF_LAZY);
- nr_failed = migrate_pages(&pagelist, new_vma_page,
- NULL, (unsigned long)vma,
- MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
+ nr_failed = migrate_pages(&pagelist, new_page, NULL,
+ start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
if (nr_failed)
putback_movable_pages(&pagelist);
}
--
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