rbd: fix leak of format 2 snapshot names

When the snapshot context for an rbd device gets updated (or the
initial one is recorded) a a list of snapshot structures is created
to represent them, one entry per snapshot.  Each entry includes a
dynamically-allocated copy of the snapshot name.

Currently the name is allocated in rbd_snap_create(), as a duplicate
of the passed-in name.

For format 1 images, the snapshot name provided is just a pointer to
an existing name.  But for format 2 images, the passed-in name is
already dynamically allocated, and in the the process of duplicating
it here we are leaking the passed-in name.

Fix this by dynamically allocating the name for format 1 snapshots
also, and then stop allocating a duplicate in rbd_snap_create().

Change rbd_dev_v1_snap_info() so none of its parameters is
side-effected unless it's going to return success.

This is part of:
    http://tracker.ceph.com/issues/4803

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 916741b09aaa49e1db05abb3618b5f3b6f7caee6..c15bb3f5ebfba03fc6c99998452b1b8967c759ba 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3427,46 +3427,44 @@ static struct rbd_snap *rbd_snap_create(struct rbd_device *rbd_dev,
                                                u64 snap_features)
 {
        struct rbd_snap *snap;
-       int ret;
 
        snap = kzalloc(sizeof (*snap), GFP_KERNEL);
        if (!snap)
                return ERR_PTR(-ENOMEM);
 
-       ret = -ENOMEM;
-       snap->name = kstrdup(snap_name, GFP_KERNEL);
-       if (!snap->name)
-               goto err;
-
+       snap->name = snap_name;
        snap->id = snap_id;
        snap->size = snap_size;
        snap->features = snap_features;
 
        return snap;
-
-err:
-       kfree(snap->name);
-       kfree(snap);
-
-       return ERR_PTR(ret);
 }
 
+/*
+ * Returns a dynamically-allocated snapshot name if successful, or a
+ * pointer-coded error otherwise.
+ */
 static char *rbd_dev_v1_snap_info(struct rbd_device *rbd_dev, u32 which,
                u64 *snap_size, u64 *snap_features)
 {
        char *snap_name;
+       int i;
 
        rbd_assert(which < rbd_dev->header.snapc->num_snaps);
 
-       *snap_size = rbd_dev->header.snap_sizes[which];
-       *snap_features = 0;     /* No features for v1 */
-
        /* Skip over names until we find the one we are looking for */
 
        snap_name = rbd_dev->header.snap_names;
-       while (which--)
+       for (i = 0; i < which; i++)
                snap_name += strlen(snap_name) + 1;
 
+       snap_name = kstrdup(snap_name, GFP_KERNEL);
+       if (!snap_name)
+               return ERR_PTR(-ENOMEM);
+
+       *snap_size = rbd_dev->header.snap_sizes[which];
+       *snap_features = 0;     /* No features for v1 */
+
        return snap_name;
 }