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

[zhouxinxing <xinxing2zhou@gmail.com>]

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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
>
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