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Date: Fri, 20 Jun 2014 17:12:53 -0400
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To: Hugh Dickins <hughd@...gle.com>
Cc: Christoph Lameter <cl@...two.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: kernel BUG at /src/linux-dev/mm/mempolicy.c:1738! on v3.16-rc1
On Fri, Jun 20, 2014 at 01:03:58PM -0700, Hugh Dickins wrote:
> 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 <n-horiguchi@...jp.nec.com>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Cc: stable@...r.kernel.org # 2.6.34+
With your patch, the bug doesn't reproduce in one hour testing. I think
it's long enough because it took only a few minutes until the reproducer
triggered the bug without your patch.
So I think the problem was gone, thank you very much!
Tested-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> ---
>
> 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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