2013-08-06 04:07:29

by Jianguo Wu

Subject: [PATCH] mm/mempolicy: return NULL if node is NUMA_NO_NODE in get_task_policy

If node == NUMA_NO_NODE, pol is NULL, we should return NULL instead of
do "if (!pol->mode)" check.

Signed-off-by: Jianguo Wu <[email protected]>
---
mm/mempolicy.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4baf12e..e0e3398 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -129,6 +129,8 @@ static struct mempolicy *get_task_policy(struct task_struct *p)
node = numa_node_id();
if (node != NUMA_NO_NODE)
pol = &preferred_node_policy[node];
+ else
+ return NULL;

/* preferred_node_policy is not initialised early in boot */
if (!pol->mode)
--
1.8.2.2

2013-08-06 21:03:29

by Andrew Morton

Subject: Re: [PATCH] mm/mempolicy: return NULL if node is NUMA_NO_NODE in get_task_policy

On Tue, 6 Aug 2013 12:06:56 +0800 Jianguo Wu <[email protected]> wrote:

> If node == NUMA_NO_NODE, pol is NULL, we should return NULL instead of
> do "if (!pol->mode)" check.
>
> Signed-off-by: Jianguo Wu <[email protected]>
> ---
> mm/mempolicy.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 4baf12e..e0e3398 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -129,6 +129,8 @@ static struct mempolicy *get_task_policy(struct task_struct *p)
> node = numa_node_id();
> if (node != NUMA_NO_NODE)
> pol = &preferred_node_policy[node];
> + else
> + return NULL;
>
> /* preferred_node_policy is not initialised early in boot */
> if (!pol->mode)

Well yes, it'll dereference a null pointer

This is neater, I think:

--- a/mm/mempolicy.c~mm-mempolicy-return-null-if-node-is-numa_no_node-in-get_task_policy
+++ a/mm/mempolicy.c
@@ -123,16 +123,19 @@ static struct mempolicy preferred_node_p
static struct mempolicy *get_task_policy(struct task_struct *p)
{
struct mempolicy *pol = p->mempolicy;
- int node;

if (!pol) {
- node = numa_node_id();
- if (node != NUMA_NO_NODE)
- pol = &preferred_node_policy[node];
+ int node = numa_node_id();

- /* preferred_node_policy is not initialised early in boot */
- if (!pol->mode)
- pol = NULL;
+ if (node != NUMA_NO_NODE) {
+ pol = &preferred_node_policy[node];
+ /*
+ * preferred_node_policy is not initialised early in
+ * boot
+ */
+ if (!pol->mode)
+ pol = NULL;
+ }
}

return pol;
_

2013-08-07 00:55:13

by Jianguo Wu

Subject: Re: [PATCH] mm/mempolicy: return NULL if node is NUMA_NO_NODE in get_task_policy

Hi Andrew,

On 2013/8/7 5:03, Andrew Morton wrote:

> On Tue, 6 Aug 2013 12:06:56 +0800 Jianguo Wu <[email protected]> wrote:
>
>> If node == NUMA_NO_NODE, pol is NULL, we should return NULL instead of
>> do "if (!pol->mode)" check.
>>
>> Signed-off-by: Jianguo Wu <[email protected]>
>> ---
>> mm/mempolicy.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index 4baf12e..e0e3398 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -129,6 +129,8 @@ static struct mempolicy *get_task_policy(struct task_struct *p)
>> node = numa_node_id();
>> if (node != NUMA_NO_NODE)
>> pol = &preferred_node_policy[node];
>> + else
>> + return NULL;
>>
>> /* preferred_node_policy is not initialised early in boot */
>> if (!pol->mode)
>
> Well yes, it'll dereference a null pointer
>
> This is neater, I think:
>

Yes, this is more readable, Thanks.

> --- a/mm/mempolicy.c~mm-mempolicy-return-null-if-node-is-numa_no_node-in-get_task_policy
> +++ a/mm/mempolicy.c
> @@ -123,16 +123,19 @@ static struct mempolicy preferred_node_p
> static struct mempolicy *get_task_policy(struct task_struct *p)
> {
> struct mempolicy *pol = p->mempolicy;
> - int node;
>
> if (!pol) {
> - node = numa_node_id();
> - if (node != NUMA_NO_NODE)
> - pol = &preferred_node_policy[node];
> + int node = numa_node_id();
>
> - /* preferred_node_policy is not initialised early in boot */
> - if (!pol->mode)
> - pol = NULL;
> + if (node != NUMA_NO_NODE) {
> + pol = &preferred_node_policy[node];
> + /*
> + * preferred_node_policy is not initialised early in
> + * boot
> + */
> + if (!pol->mode)
> + pol = NULL;
> + }
> }
>
> return pol;
> _
>
>
> .
>