From: Daniel Dawson <danielcdawson@gmail.com>
Date: Wed, 9 Jan 2019 04:27:35 +0000 (-0800)
Subject: Fix data corruption leading to kernel panic.
X-Git-Tag: v0.8.2~3^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F470%2Fhead;p=thirdparty%2Fsnapper.git

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 f5fda6be..8c31c721 100644
--- 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;