[PATCH parted 2/2] _device_unregister: check for unregistering the same device twice

[Hans de Goede]

_device_unregister() can get called 2 times for the same device if
a libparted user explictly removes the device from the cache using
ped_device_cache_remove(), it gets called and it then becomes the
user's responsibility to free the PedDevice by calling
ped_device_destroy(). ped_device_destroy() will then call
_device_unregister() a second time with the same device, so if the
device is not found in the list do nothing.

* libparted/device.c(_device_unregister): check for unregistering
the same device twice.
---
 NEWS               |    3 +++
 libparted/device.c |   10 ++++++++++
 2 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/NEWS b/NEWS
index ddbc893..77d893a 100644
--- a/NEWS
+++ b/NEWS
@@ -29,6 +29,9 @@ GNU parted NEWS                                    -*- 
outline -*-
   libparted now properly checks the return value of dm_task_run when
   operating on devicemapper devices.
 
+  allow using ped_device_cache_remove(dev) followed by a (later)
+  ped_device_destroy() without corrupting the device cache.
+
 ** Changes in behavior
 
   libparted no longer issues an exception/warning about >512-byte
diff --git a/libparted/device.c b/libparted/device.c
index f20121b..00f49a3 100644
--- a/libparted/device.c
+++ b/libparted/device.c
@@ -73,6 +73,16 @@ _device_unregister (PedDevice* dev)
                if (walk == dev) break;
        }
 
+       /* We can get called 2 times for the same device if a libparted user
+          explictly removes the device from the cache using
+          ped_device_cache_remove(), we get called and it then becomes the
+          user's responsibility to free the PedDevice by calling
+          ped_device_destroy().
+          ped_device_destroy() will then call us a second time, so if the
+          device is not found in the list do nothing. */
+       if (walk == NULL)
+               return;
+
        if (last)
                last->next = dev->next;
        else
-- 
1.7.0.1