Fix data corruption leading to kernel panic.

I found that trying to use Snapper to create a Btrfs snapshot with a qgroup set causes the system to lock up, sometimes with a kernel panic message on the console. I tracked down the problem to this code. As it currently stands, `buffer` goes out of scope before the `ioctl` call can use it, and in my case, at least, it seems some of the data is already overwritten. Moving it out of the `if` statement lets this work properly.

diff --git a/snapper/BtrfsUtils.cc b/snapper/BtrfsUtils.cc
index f5fda6be260ecb8a8c8927fe4329b928372b7fd5..8c31c721698a880a8ab59196a8ec569dc9ef97e0 100644 (file)
--- a/snapper/BtrfsUtils.cc
+++ b/snapper/BtrfsUtils.cc
@@ -143,10 +143,11 @@ namespace snapper
 
 #ifdef ENABLE_BTRFS_QUOTA
 
+           size_t size = sizeof(btrfs_qgroup_inherit) + sizeof(((btrfs_qgroup_inherit*) 0)->qgroups[0]);
+           vector<char> buffer(size, 0);
+        
            if (qgroup != no_qgroup)
            {
-               size_t size = sizeof(btrfs_qgroup_inherit) + sizeof(((btrfs_qgroup_inherit*) 0)->qgroups[0]);
-               vector<char> buffer(size, 0);
                struct btrfs_qgroup_inherit* inherit = (btrfs_qgroup_inherit*) &buffer[0];
 
                inherit->num_qgroups = 1;