2018-03-09 05:24:32

by Yisheng Xie

Subject: [PATCH] mm/mempolicy: Avoid use uninitialized preferred_node

Alexander reported an use of uninitialized memory in __mpol_equal(),
which is caused by incorrect use of preferred_node.

When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it use
numa_node_id() instead of preferred_node, however, __mpol_equeue() use
preferred_node without check whether it is MPOL_F_LOCAL or not.

Reported-by: Alexander Potapenko <[email protected]>
Signed-off-by: Yisheng Xie <[email protected]>
---
mm/mempolicy.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d879f1d..641545e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2124,6 +2124,9 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
case MPOL_INTERLEAVE:
return !!nodes_equal(a->v.nodes, b->v.nodes);
case MPOL_PREFERRED:
+ /* a's flags is the same as b's */
+ if (a->flags & MPOL_F_LOCAL)
+ return true;
return a->v.preferred_node == b->v.preferred_node;
default:
BUG();
--
1.8.3.1

2018-03-09 10:52:26

by Alexander Potapenko

Subject: Re: [PATCH] mm/mempolicy: Avoid use uninitialized preferred_node

On Fri, Mar 9, 2018 at 6:21 AM, Yisheng Xie <[email protected]> wrote:
> Alexander reported an use of uninitialized memory in __mpol_equal(),
> which is caused by incorrect use of preferred_node.
>
> When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it use
> numa_node_id() instead of preferred_node, however, __mpol_equeue() use
> preferred_node without check whether it is MPOL_F_LOCAL or not.
>
> Reported-by: Alexander Potapenko <[email protected]>
> Signed-off-by: Yisheng Xie <[email protected]>
Tested-by: Alexander Potapenko <[email protected]>

I confirm that the patch fixes the problem. Thanks for the quick turnaround!
Any idea which commit had introduced the bug in the first place?
> ---
> mm/mempolicy.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index d879f1d..641545e 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2124,6 +2124,9 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
> case MPOL_INTERLEAVE:
> return !!nodes_equal(a->v.nodes, b->v.nodes);
> case MPOL_PREFERRED:
> + /* a's flags is the same as b's */
> + if (a->flags & MPOL_F_LOCAL)
> + return true;
> return a->v.preferred_node == b->v.preferred_node;
> default:
> BUG();
> --
> 1.8.3.1
>



--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

2018-03-09 11:12:06

by Yisheng Xie

Subject: Re: [PATCH] mm/mempolicy: Avoid use uninitialized preferred_node

Hi Alexander ,

On 2018/3/9 18:49, Alexander Potapenko wrote:
> On Fri, Mar 9, 2018 at 6:21 AM, Yisheng Xie <[email protected]> wrote:
>> Alexander reported an use of uninitialized memory in __mpol_equal(),
>> which is caused by incorrect use of preferred_node.
>>
>> When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it use
>> numa_node_id() instead of preferred_node, however, __mpol_equeue() use
>> preferred_node without check whether it is MPOL_F_LOCAL or not.
>>
>> Reported-by: Alexander Potapenko <[email protected]>
>> Signed-off-by: Yisheng Xie <[email protected]>
> Tested-by: Alexander Potapenko <[email protected]>

Thanks,
>
> I confirm that the patch fixes the problem. Thanks for the quick turnaround!
> Any idea which commit had introduced the bug in the first place?

IIUC, It is introduce by:
Fixes: fc36b8d3d819 (mempolicy: use MPOL_F_LOCAL to Indicate Preferred Local Policy)

Thanks
Yisheng
>> ---
>> mm/mempolicy.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index d879f1d..641545e 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -2124,6 +2124,9 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
>> case MPOL_INTERLEAVE:
>> return !!nodes_equal(a->v.nodes, b->v.nodes);
>> case MPOL_PREFERRED:
>> + /* a's flags is the same as b's */
>> + if (a->flags & MPOL_F_LOCAL)
>> + return true;
>> return a->v.preferred_node == b->v.preferred_node;
>> default:
>> BUG();
>> --
>> 1.8.3.1
>>
>
>
>