mtd: mtdblock: introduce mtdblks_lock

The mtdblks array and its content are prone to race conditions. Introduce
the mutex mtdblks_lock in order to solve this.

[Amended by Artem Bityutskiy]

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index 208c6faa0358..77db5ce24d92 100644
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -29,6 +29,8 @@ static struct mtdblk_dev {
         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
 } *mtdblks[MAX_MTD_DEVICES];
 
+static struct mutex mtdblks_lock;
+
 /*
  * Cache stuff...
  *
@@ -270,15 +272,19 @@ static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 
         DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
 
+        mutex_lock(&mtdblks_lock);
         if (mtdblks[dev]) {
                 mtdblks[dev]->count++;
+                mutex_unlock(&mtdblks_lock);
                 return 0;
         }
 
         /* OK, it's not open. Create cache info for it */
         mtdblk = kzalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
-        if (!mtdblk)
+        if (!mtdblk) {
+                mutex_unlock(&mtdblks_lock);
                 return -ENOMEM;
+        }
 
         mtdblk->count = 1;
         mtdblk->mtd = mtd;
@@ -291,6 +297,7 @@ static int mtdblock_open(struct mtd_blktrans_dev *mbd)
         }
 
         mtdblks[dev] = mtdblk;
+        mutex_unlock(&mtdblks_lock);
 
         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 
@@ -304,6 +311,8 @@ static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 
         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
 
+        mutex_lock(&mtdblks_lock);
+
         mutex_lock(&mtdblk->cache_mutex);
         write_cached_data(mtdblk);
         mutex_unlock(&mtdblk->cache_mutex);
@@ -316,6 +325,9 @@ static int mtdblock_release(struct mtd_blktrans_dev *mbd)
                 vfree(mtdblk->cache_data);
                 kfree(mtdblk);
         }
+
+        mutex_unlock(&mtdblks_lock);
+
         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 
         return 0;
@@ -376,6 +388,8 @@ static struct mtd_blktrans_ops mtdblock_tr = {
 
 static int __init init_mtdblock(void)
 {
+        mutex_init(&mtdblks_lock);
+
         return register_mtd_blktrans(&mtdblock_tr);
 }