[PATCH] cfag12864b: fix crash when built-in and no parport present

The problem comes when ks0108/cfag12864b are built-in and no parallel port is
present.  ks0108_init() is called first, as it should be, but fails to load
(as there is no parallel port to use).

After that, cfag12864b_init() gets called, without knowing anything about
ks0108 failed, and calls ks0108_writecontrol(), which dereferences an
uninitialized pointer.

Init order is OK, I think.  The problem is how to stop cfag12864b_init() being
called if ks0108 failed to load.  modprobe does it for us, but, how when
built-in?

Signed-off-by: Miguel Ojeda Sandonis <maxextreme@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/auxdisplay/cfag12864b.c b/drivers/auxdisplay/cfag12864b.c
index 889583dfc1a6..cb44cb4f6a47 100644
--- a/drivers/auxdisplay/cfag12864b.c
+++ b/drivers/auxdisplay/cfag12864b.c
@@ -312,6 +312,17 @@ EXPORT_SYMBOL_GPL(cfag12864b_disable);
 EXPORT_SYMBOL_GPL(cfag12864b_isenabled);
 
 /*
+ * Is the module inited?
+ */
+
+static unsigned char cfag12864b_inited;
+unsigned char cfag12864b_isinited(void)
+{
+        return cfag12864b_inited;
+}
+EXPORT_SYMBOL_GPL(cfag12864b_isinited);
+
+/*
  * Module Init & Exit
  */
 
@@ -319,6 +330,13 @@ static int __init cfag12864b_init(void)
 {
         int ret = -EINVAL;
 
+        /* ks0108_init() must be called first */
+        if (!ks0108_isinited()) {
+                printk(KERN_ERR CFAG12864B_NAME ": ERROR: "
+                        "ks0108 is not initialized\n");
+                goto none;
+        }
+
         if (PAGE_SIZE < CFAG12864B_SIZE) {
                 printk(KERN_ERR CFAG12864B_NAME ": ERROR: "
                         "page size (%i) < cfag12864b size (%i)\n",
@@ -354,6 +372,7 @@ static int __init cfag12864b_init(void)
         cfag12864b_clear();
         cfag12864b_on();
 
+        cfag12864b_inited = 1;
         return 0;
 
 cachealloced: