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>

1 files changed, 24 insertions, 25 deletions

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 63980722db41..5e237f630c47 100644
--- 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);
         }