[PATCH] mm/mempolicy: Avoid use uninitialized preferred_node

[PATCH] mm/mempolicy: Avoid use uninitialized preferred_node

[Yisheng Xie]

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 <glider@google.com>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
---
 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

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

[Alexander Potapenko]

On Fri, Mar 9, 2018 at 6:21 AM, Yisheng Xie <xieyisheng1@huawei.com> 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 <glider@google.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Tested-by: Alexander Potapenko <glider@google.com>

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

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

[Yisheng Xie]

Hi Alexander ,

On 2018/3/9 18:49, Alexander Potapenko wrote:
> On Fri, Mar 9, 2018 at 6:21 AM, Yisheng Xie <xieyisheng1@huawei.com> 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 <glider@google.com>
>> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
> Tested-by: Alexander Potapenko <glider@google.com>

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
>>
> 
> 
>