3 files changed, 35 insertions, 12 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 62479ac4baf7..70bb0e8b62ce 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1105,6 +1105,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         int i;
         int r = -EINVAL;
         char *origin_path, *cow_path;
+        dev_t origin_dev, cow_dev;
         unsigned args_used, num_flush_bios = 1;
         fmode_t origin_mode = FMODE_READ;
 
@@ -1135,11 +1136,19 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                 ti->error = "Cannot get origin device";
                 goto bad_origin;
         }
+        origin_dev = s->origin->bdev->bd_dev;
 
         cow_path = argv[0];
         argv++;
         argc--;
 
+        cow_dev = dm_get_dev_t(cow_path);
+        if (cow_dev && cow_dev == origin_dev) {
+                ti->error = "COW device cannot be the same as origin device";
+                r = -EINVAL;
+                goto bad_cow;
+        }
+
         r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
         if (r) {
                 ti->error = "Cannot get COW device";
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 7210e5392cc4..f9e8f0bef332 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -365,6 +365,26 @@ static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
 }
 
 /*
+ * Convert the path to a device
+ */
+dev_t dm_get_dev_t(const char *path)
+{
+        dev_t uninitialized_var(dev);
+        struct block_device *bdev;
+
+        bdev = lookup_bdev(path);
+        if (IS_ERR(bdev))
+                dev = name_to_dev_t(path);
+        else {
+                dev = bdev->bd_dev;
+                bdput(bdev);
+        }
+
+        return dev;
+}
+EXPORT_SYMBOL_GPL(dm_get_dev_t);
+
+/*
  * Add a device to the list, or just increment the usage count if
  * it's already present.
  */
@@ -372,23 +392,15 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
                   struct dm_dev **result)
 {
         int r;
-        dev_t uninitialized_var(dev);
+        dev_t dev;
         struct dm_dev_internal *dd;
         struct dm_table *t = ti->table;
-        struct block_device *bdev;
 
         BUG_ON(!t);
 
-        /* convert the path to a device */
-        bdev = lookup_bdev(path);
-        if (IS_ERR(bdev)) {
-                dev = name_to_dev_t(path);
-                if (!dev)
-                        return -ENODEV;
-        } else {
-                dev = bdev->bd_dev;
-                bdput(bdev);
-        }
+        dev = dm_get_dev_t(path);
+        if (!dev)
+                return -ENODEV;
 
         dd = find_device(&t->devices, dev);
         if (!dd) {
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 82ae3b5e2c45..0830c9e86f0d 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -124,6 +124,8 @@ struct dm_dev {
         char name[16];
 };
 
+dev_t dm_get_dev_t(const char *path);
+
 /*
  * Constructors should call these functions to ensure destination devices
  * are opened/closed correctly.