[PATCH] mm: numa: fix NULL pointer dereference

[PATCH] mm: numa: fix NULL pointer dereference

[Mauro Dreissig]

From: Mauro Dreissig <mukadr@gmail.com>

The "pol->mode" field is accessed even when no mempolicy
is assigned to the "pol" variable.

Signed-off-by: Mauro Dreissig <mukadr@gmail.com>
---
 mm/mempolicy.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 6b1d426..105fff0 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -127,12 +127,16 @@ static struct mempolicy *get_task_policy(struct task_struct *p)
 
 	if (!pol) {
 		node = numa_node_id();
-		if (node != NUMA_NO_NODE)
+		if (node != NUMA_NO_NODE) {
 			pol = &preferred_node_policy[node];
 
-		/* preferred_node_policy is not initialised early in boot */
-		if (!pol->mode)
-			pol = NULL;
+			/*
+			 * preferred_node_policy is not initialised early
+			 * in boot
+			 */
+			if (!pol->mode)
+				pol = NULL;
+		}
 	}
 
 	return pol;
-- 
1.8.1.2

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Re: [PATCH] mm: numa: fix NULL pointer dereference

[zhouxinxing]

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Is it possible to check pol if it is equal to NULL prior to access to mode field?

Mauro Dreissig <mukadr@gmail.com> wrote:

>From: Mauro Dreissig <mukadr@gmail.com>
>
>The "pol->mode" field is accessed even when no mempolicy
>is assigned to the "pol" variable.
>
>Signed-off-by: Mauro Dreissig <mukadr@gmail.com>
>---
> mm/mempolicy.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
>diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>index 6b1d426..105fff0 100644
>--- a/mm/mempolicy.c
>+++ b/mm/mempolicy.c
>@@ -127,12 +127,16 @@ static struct mempolicy *get_task_policy(struct
>task_struct *p)
> 
> 	if (!pol) {
> 		node = numa_node_id();
>-		if (node != NUMA_NO_NODE)
>+		if (node != NUMA_NO_NODE) {
> 			pol = &preferred_node_policy[node];
> 
>-		/* preferred_node_policy is not initialised early in boot */
>-		if (!pol->mode)
>-			pol = NULL;
>+			/*
>+			 * preferred_node_policy is not initialised early
>+			 * in boot
>+			 */
>+			if (!pol->mode)
>+				pol = NULL;
>+		}
> 	}
> 
> 	return pol;
>-- 
>1.8.1.2
>
>--
>To unsubscribe, send a message with 'unsubscribe linux-mm' in
>the body to majordomo@kvack.org.  For more info on Linux MM,
>see: http://www.linux-mm.org/ .
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-- 
Sent from my Android device with Gmail Plus. Please excuse my brevity.

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Re: [PATCH] mm: numa: fix NULL pointer dereference

[Mauro Dreissig]

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2013/8/6 Mauro Dreissig <mukadr@gmail.com>

> From: Mauro Dreissig <mukadr@gmail.com>
>
> The "pol->mode" field is accessed even when no mempolicy
> is assigned to the "pol" variable.
>
> Signed-off-by: Mauro Dreissig <mukadr@gmail.com>
> ---
>  mm/mempolicy.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 6b1d426..105fff0 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -127,12 +127,16 @@ static struct mempolicy *get_task_policy(struct
> task_struct *p)
>
>         if (!pol) {
>                 node = numa_node_id();
> -               if (node != NUMA_NO_NODE)
> +               if (node != NUMA_NO_NODE) {
>                         pol = &preferred_node_policy[node];
>
> -               /* preferred_node_policy is not initialised early in boot
> */
> -               if (!pol->mode)
> -                       pol = NULL;
> +                       /*
> +                        * preferred_node_policy is not initialised early
> +                        * in boot
> +                        */
> +                       if (!pol->mode)
> +                               pol = NULL;
> +               }
>         }
>
>         return pol;
> --
> 1.8.1.2
>
>
A patch about this issue already exist, please ignore my message.

http://marc.info/?l=linux-mm&m=137576205227365&w=2

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