[Xen-devel] [PATCH 03/16] blkfront: don't access freed struct xenbus_device

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Jan Beulich <jbeulich@xxxxxxxxxx>

Unfortunately commit "blkfront: fixes for 'xm block-detach ... --force'"
still wasn't quite right - there was a reference to freed memory left
from blkfront_closing().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 drivers/block/xen-blkfront.c |   25 ++++++++++++-------------
 1 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index b1b16e5..df2bae5 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -981,13 +981,11 @@ static void blkfront_connect(struct blkfront_info *info)
  * the backend.  Once is this done, we can switch to Closed in
  * acknowledgement.
  */
-static void blkfront_closing(struct xenbus_device *dev)
+static void blkfront_closing(struct blkfront_info *info)
 {
-       struct blkfront_info *info = dev_get_drvdata(&dev->dev);
        unsigned int minor, nr_minors;
        unsigned long flags;
 
-       dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
 
        if (info->rq == NULL)
                goto out;
@@ -1013,7 +1011,8 @@ static void blkfront_closing(struct xenbus_device *dev)
        xlbd_release_minors(minor, nr_minors);
 
  out:
-       xenbus_frontend_closed(dev);
+       if (info->xbdev)
+               xenbus_frontend_closed(info->xbdev);
 }
 
 /**
@@ -1053,7 +1052,7 @@ static void blkback_changed(struct xenbus_device *dev,
                        xenbus_dev_error(dev, -EBUSY,
                                         "Device in use; refusing to close");
                else
-                       blkfront_closing(dev);
+                       blkfront_closing(info);
                mutex_unlock(&bd->bd_mutex);
                bdput(bd);
                break;
@@ -1071,7 +1070,7 @@ static int blkfront_remove(struct xenbus_device *dev)
        if(info->users == 0)
                kfree(info);
        else
-               info->is_ready = -1;
+               info->xbdev = NULL;
 
        return 0;
 }
@@ -1080,14 +1079,14 @@ static int blkfront_is_ready(struct xenbus_device *dev)
 {
        struct blkfront_info *info = dev_get_drvdata(&dev->dev);
 
-       return info->is_ready > 0;
+       return info->is_ready && info->xbdev;
 }
 
 static int blkif_open(struct block_device *bdev, fmode_t mode)
 {
        struct blkfront_info *info = bdev->bd_disk->private_data;
 
-       if(info->is_ready < 0)
+       if (!info->xbdev)
                return -ENODEV;
        info->users++;
        return 0;
@@ -1102,13 +1101,13 @@ static int blkif_release(struct gendisk *disk, fmode_t 
mode)
                   have ignored this request initially, as the device was
                   still mounted. */
                struct xenbus_device *dev = info->xbdev;
-               enum xenbus_state state = 
xenbus_read_driver_state(dev->otherend);
 
-               if(info->is_ready < 0) {
-                       blkfront_closing(dev);
+               if (!dev) {
+                       blkfront_closing(info);
                        kfree(info);
-               } else if (state == XenbusStateClosing && info->is_ready)
-                       blkfront_closing(dev);
+               } else if (xenbus_read_driver_state(dev->otherend)
+                          == XenbusStateClosing && info->is_ready)
+                       blkfront_closing(info);
        }
        return 0;
 }
-- 
1.7.1.1


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