[PATCH] Fix the kernel panic of audit_filter_task when key field is set

[zhangxiliang <zhangxiliang@cn.fujitsu.com>]

When calling audit_filter_task(), it calls audit_filter_rules() with audit_context is NULL.
If the key field is set, the result in audit_filter_rules() will be set to 1 and 
ctx->filterkey will be set to key.
But the ctx is NULL in this condition, so kernel will panic.

Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
---
 kernel/auditsc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4699950..012c94e 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -610,7 +610,7 @@ static int audit_filter_rules(struct task_struct *tsk,
 		if (!result)
 			return 0;
 	}
-	if (rule->filterkey)
+	if (rule->filterkey && ctx)
 		ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
 	switch (rule->action) {
 	case AUDIT_NEVER:    *state = AUDIT_DISABLED;	    break;