[Xen-devel] [PATCH] xen-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>

---
 drivers/block/xen-blkback/xenbus.c |   49 ++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

--- 3.7/drivers/block/xen-blkback/xenbus.c
+++ 3.7-xen-blkback-mode-leak/drivers/block/xen-blkback/xenbus.c
@@ -366,6 +366,7 @@ static int xen_blkbk_remove(struct xenbu
                be->blkif = NULL;
        }
 
+       kfree(be->mode);
        kfree(be);
        dev_set_drvdata(&dev->dev, NULL);
        return 0;
@@ -501,6 +502,7 @@ 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("");
@@ -520,10 +522,10 @@ static void backend_changed(struct xenbu
                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;
        }
 
@@ -541,36 +543,33 @@ 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. */
+       err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
+       if (err)
+               return;
 
-               char *p = strrchr(dev->otherend, '/') + 1;
-               long handle;
-               err = strict_strtoul(p, 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);
        }

Attachment: linux-3.7-xen-blkback-mode-leak.patch
Description: Text document

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