[gparted] Check usability of named device following a non-existent / invalid one (#756434)

[Curtis Gedak <gedakc src gnome org>]

commit 9d6ebb3dabafc7bfb0105bb5758e04a5efe85e6f
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Wed Oct 14 17:51:38 2015 +0100

    Check usability of named device following a non-existent / invalid one (#756434)
    
    When multiple devices are named on the command line and (after sorting
    and removing duplicates) the device following a non-existent or invalid
    one is not checked for usability [1].  In most situations this isn't
    noticed as the device gets skipped at the "Searching ...  partitions"
    step instead.  However as seen in bug 755495 and commit [2]
    checking usability matters.
    
    For example (on CentOS 6.5) a large sector disk device can be edited
    when it follows a non-existent or invalid device named on the command
    line:
    
        # modprobe scsi_debug dev_size_mb=128 sector_size=4096
        # fgrep scsi_debug /sys/block/*/device/model
        /sys/block/sdd/device/model:scsi_debug
    
        # ./gpartedbin /dev/does-not-exist /dev/sdd
        ======================
        libparted : 2.1
        ======================
        Could not stat device /dev/does-not-exist - No such file or directory.
        Device /dev/sdd has a logical sector size of 4096.  Not all parts of GNU Parted support this at the 
moment, and the working code is HIGHLY EXPERIMENTAL.
    
        /dev/sdd: unrecognised disk label
    
    When erasing a device don't skip confirming the following device is
    usable.
    
    [1] Usable device as implemented by useable_device()
        Must not have a large sector size when GParted is built with an old
        version of libparted which doesn't support large sector sizes and
        must be able to read the first sector.
    
    [2] 362b2db331b4c31a978bb67232fa7f3ce9ab38c3
        Check disks named on the command line are safe to use too (#755495)
    
    Bug 756434 - GParted dumps core when passing non-existent or invalid
                 device on the command line

 src/GParted_Core.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/GParted_Core.cc b/src/GParted_Core.cc
index 8f6be31..ee97efa 100644
--- a/src/GParted_Core.cc
+++ b/src/GParted_Core.cc
@@ -255,7 +255,7 @@ void GParted_Core::set_devices_thread( std::vector<Device> * pdevices )
                        if ( lp_device == NULL || ! useable_device( lp_device ) )
                        {
                                // Remove this disk device which isn't useable
-                               device_paths.erase( device_paths.begin() + t );
+                               device_paths.erase( device_paths.begin() + t-- );
                        }
                }
        }