zfs_handle used after being closed/freed in change_one callback

This is a typical case of use after free. We would call zfs_close(zhp)
which would free the handle, and then call zfs_iter_children() on that
handle later.  This change ensures that the zfs_handle is only closed
when we are ready to return.

Running `zfs inherit -r sharenfs pool` was failing with an error
code without any error messages. After some debugging I've pinpointed
the issue to be memory corruption, which would cause zfs to try to
issue an ioctl to the wrong device and receive ENOTTY.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alek Pinchuk <apinchuk@datto.com>
Signed-off-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Issue #7967
Closes #9165

diff --git a/lib/libzfs/libzfs_changelist.c b/lib/libzfs/libzfs_changelist.c
index 3101febc160518a456bfdca7d71b94dd3ccb2cc8..72f641056edc64a3e4489718af0b6f10a9e16093 100644 (file)
--- a/lib/libzfs/libzfs_changelist.c
+++ b/lib/libzfs/libzfs_changelist.c
@@ -475,9 +475,10 @@ change_one(zfs_handle_t *zhp, void *data)
        prop_changelist_t *clp = data;
        char property[ZFS_MAXPROPLEN];
        char where[64];
-       prop_changenode_t *cn;
+       prop_changenode_t *cn = NULL;
        zprop_source_t sourcetype = ZPROP_SRC_NONE;
        zprop_source_t share_sourcetype = ZPROP_SRC_NONE;
+       int ret = 0;
 
        /*
         * We only want to unmount/unshare those filesystems that may inherit
@@ -493,8 +494,7 @@ change_one(zfs_handle_t *zhp, void *data)
            zfs_prop_get(zhp, clp->cl_prop, property,
            sizeof (property), &sourcetype, where, sizeof (where),
            B_FALSE) != 0) {
-               zfs_close(zhp);
-               return (0);
+               goto out;
        }
 
        /*
@@ -506,8 +506,7 @@ change_one(zfs_handle_t *zhp, void *data)
            zfs_prop_get(zhp, clp->cl_shareprop, property,
            sizeof (property), &share_sourcetype, where, sizeof (where),
            B_FALSE) != 0) {
-               zfs_close(zhp);
-               return (0);
+               goto out;
        }
 
        if (clp->cl_alldependents || clp->cl_allchildren ||
@@ -518,8 +517,8 @@ change_one(zfs_handle_t *zhp, void *data)
            share_sourcetype == ZPROP_SRC_INHERITED))) {
                if ((cn = zfs_alloc(zfs_get_handle(zhp),
                    sizeof (prop_changenode_t))) == NULL) {
-                       zfs_close(zhp);
-                       return (-1);
+                       ret = -1;
+                       goto out;
                }
 
                cn->cn_handle = zhp;
@@ -541,16 +540,23 @@ change_one(zfs_handle_t *zhp, void *data)
                        uu_avl_insert(clp->cl_tree, cn, idx);
                } else {
                        free(cn);
-                       zfs_close(zhp);
+                       cn = NULL;
                }
 
                if (!clp->cl_alldependents)
-                       return (zfs_iter_children(zhp, change_one, data));
-       } else {
-               zfs_close(zhp);
+                       ret = zfs_iter_children(zhp, change_one, data);
+
+               /*
+                * If we added the handle to the changelist, we will re-use it
+                * later so return without closing it.
+                */
+               if (cn != NULL)
+                       return (ret);
        }
 
-       return (0);
+out:
+       zfs_close(zhp);
+       return (ret);
 }
 
 static int