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

[zhouxinxing <xinxing2zhou@xxxxxxxxx>]

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

Mauro Dreissig <mukadr@xxxxxxxxx> wrote:

From: Mauro Dreissig <mukadr@xxxxxxxxx>

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

Signed-off-by: Mauro Dreissig <mukadr@xxxxxxxxx>
---
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;

-- 
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