[Xen-devel] [PATCH] linux-2.6.18/blkback: do not leak mode property

["Jan Beulich" <JBeulich@xxxxxxxx>]

"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@xxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/drivers/xen/blkback/xenbus.c
+++ b/drivers/xen/blkback/xenbus.c
@@ -198,6 +198,7 @@ static int blkback_remove(struct xenbus_
                be->blkif = NULL;
        }
 
+       kfree(be->mode);
        kfree(be);
        dev->dev.driver_data = NULL;
        write_unlock(&sysfs_read_lock);
@@ -278,6 +279,7 @@ static void backend_changed(struct xenbu
                = container_of(watch, struct backend_info, backend_watch);
        struct xenbus_device *dev = be->dev;
        int cdrom = 0;
+       unsigned long handle;
        char *device_type;
 
        DPRINTK("");
@@ -295,12 +297,12 @@ static void backend_changed(struct xenbu
                return;
        }
 
-       if ((be->major || be->minor) &&
-           ((be->major != major) || (be->minor != minor))) {
-               printk(KERN_WARNING
-                      "blkback: 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)
+                       printk(KERN_WARNING "blkback: "
+                              "changing physical device (from %x:%x to "
+                              "%x:%x) not supported.\n",
+                              be->major, be->minor, major, minor);
                return;
        }
 
@@ -318,31 +320,30 @@ static void backend_changed(struct xenbu
                kfree(device_type);
        }
 
-       if (be->major == 0 && be->minor == 0) {
-               /* Front end dir is a number, which is used as the handle. */
+       /* Front end dir is a number, which is used as the handle. */
+       handle = simple_strtoul(strrchr(dev->otherend, '/') + 1, NULL, 0);
 
-               char *p = strrchr(dev->otherend, '/') + 1;
-               long handle = simple_strtoul(p, NULL, 0);
+       be->major = major;
+       be->minor = minor;
 
-               be->major = major;
-               be->minor = minor;
-
-               err = vbd_create(be->blkif, handle, major, minor,
-                                (NULL == strchr(be->mode, 'w')), cdrom);
-               if (err) {
-                       be->major = be->minor = 0;
-                       xenbus_dev_fatal(dev, err, "creating vbd structure");
-                       return;
-               }
+       err = vbd_create(be->blkif, handle, major, minor,
+                        (NULL == strchr(be->mode, 'w')), cdrom);
 
+       if (err)
+               xenbus_dev_fatal(dev, err, "creating vbd structure");
+       else {
                err = xenvbd_sysfs_addif(dev);
                if (err) {
                        vbd_free(&be->blkif->vbd);
-                       be->major = be->minor = 0;
                        xenbus_dev_fatal(dev, err, "creating sysfs entries");
-                       return;
                }
+       }
 
+       if (err) {
+               kfree(be->mode);
+               be->mode = NULL;
+               be->major = be->minor = 0;
+       } else {
                /* We're potentially connected now */
                update_blkif_status(be->blkif);
        }

Attachment: xen-blkback-mode-leak.patch
Description: Text document

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