[MTD] Fix module refcounting in NAND board drivers.

The _board_ driver needs to be mtd->owner, and it in turn pins the
nand.ko module. Fix them all to actually do that, and fix nand.ko not to
overwrite it -- and also to check that the caller sets it, if the caller
is a module.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index fdaf32083ada..42cff0a2b93d 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -69,6 +69,7 @@
  *
  */
 
+#include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
@@ -2316,11 +2317,12 @@ static void nand_resume(struct mtd_info *mtd)
  * @mtd:        MTD device structure
  * @maxchips:   Number of chips to scan for
  *
- * This fills out all the not initialized function pointers
+ * This fills out all the uninitialized function pointers
  * with the defaults.
  * The flash ID is read and the mtd/chip structures are
  * filled with the appropriate values. Buffers are allocated if
  * they are not provided by the board driver
+ * The mtd->owner field must be set to the module of the caller
  *
  */
 int nand_scan(struct mtd_info *mtd, int maxchips)
@@ -2328,6 +2330,16 @@ int nand_scan(struct mtd_info *mtd, int maxchips)
         int i, nand_maf_id, nand_dev_id, busw, maf_id;
         struct nand_chip *this = mtd->priv;
 
+        /* module_text_address() isn't exported. But if _this_ is a module,
+           it's a fairly safe bet that its caller is a module too... and
+           that means the call to module_text_address() gets optimised out
+           without having to resort to ifdefs */
+        if (!mtd->owner && (THIS_MODULE ||
+            module_text_address((unsigned long)__builtin_return_address(0)))) {
+                printk(KERN_CRIT "nand_scan() called with NULL mtd->owner!\n");
+                BUG();
+        }
+
         /* Get buswidth to select the correct functions */
         busw = this->options & NAND_BUSWIDTH_16;
 
@@ -2676,8 +2688,6 @@ int nand_scan(struct mtd_info *mtd, int maxchips)
         /* and make the autooob the default one */
         memcpy(&mtd->oobinfo, this->autooob, sizeof(mtd->oobinfo));
 
-        mtd->owner = THIS_MODULE;
-
         /* Check, if we should skip the bad block table scan */
         if (this->options & NAND_SKIP_BBTSCAN)
                 return 0;