xen-blkback: do not leak mode property

"be->mode" is obtained from xenbus_read(), which does a kmalloc() for
the message body. The short string is never released, so do it along
with freeing "be" itself, and make sure the string isn't kept when
backend_changed() doesn't complete successfully (which made it
desirable to slightly re-structure that function, so that the error
cleanup can be done in one place).

Reported-by: Olaf Hering <olaf@aepfle.de>
CC: stable@vger.kernel.org
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 63980722db41af223941be7e83b33001c89bd9c7..5e237f630c47f2b2299749e067744dc89adba1a8 100644 (file)
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -367,6 +367,7 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
                be->blkif = NULL;
        }
 
+       kfree(be->mode);
        kfree(be);
        dev_set_drvdata(&dev->dev, NULL);
        return 0;
@@ -502,6 +503,7 @@ static void backend_changed(struct xenbus_watch *watch,
                = container_of(watch, struct backend_info, backend_watch);
        struct xenbus_device *dev = be->dev;
        int cdrom = 0;
+       unsigned long handle;
        char *device_type;
 
        DPRINTK("");
@@ -521,10 +523,10 @@ static void backend_changed(struct xenbus_watch *watch,
                return;
        }
 
-       if ((be->major || be->minor) &&
-           ((be->major != major) || (be->minor != minor))) {
-               pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
-                       be->major, be->minor, major, minor);
+       if (be->major | be->minor) {
+               if (be->major != major || be->minor != minor)
+                       pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
+                               be->major, be->minor, major, minor);
                return;
        }
 
@@ -542,36 +544,33 @@ static void backend_changed(struct xenbus_watch *watch,
                kfree(device_type);
        }
 
-       if (be->major == 0 && be->minor == 0) {
-               /* Front end dir is a number, which is used as the handle. */
-
-               char *p = strrchr(dev->otherend, '/') + 1;
-               long handle;
-               err = strict_strtoul(p, 0, &handle);
-               if (err)
-                       return;
+       /* Front end dir is a number, which is used as the handle. */
+       err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
+       if (err)
+               return;
 
-               be->major = major;
-               be->minor = minor;
+       be->major = major;
+       be->minor = minor;
 
-               err = xen_vbd_create(be->blkif, handle, major, minor,
-                                (NULL == strchr(be->mode, 'w')), cdrom);
-               if (err) {
-                       be->major = 0;
-                       be->minor = 0;
-                       xenbus_dev_fatal(dev, err, "creating vbd structure");
-                       return;
-               }
+       err = xen_vbd_create(be->blkif, handle, major, minor,
+                            !strchr(be->mode, 'w'), cdrom);
 
+       if (err)
+               xenbus_dev_fatal(dev, err, "creating vbd structure");
+       else {
                err = xenvbd_sysfs_addif(dev);
                if (err) {
                        xen_vbd_free(&be->blkif->vbd);
-                       be->major = 0;
-                       be->minor = 0;
                        xenbus_dev_fatal(dev, err, "creating sysfs entries");
-                       return;
                }
+       }
 
+       if (err) {
+               kfree(be->mode);
+               be->mode = NULL;
+               be->major = 0;
+               be->minor = 0;
+       } else {
                /* We're potentially connected now */
                xen_update_blkif_status(be->blkif);
        }