Fix use after free in close_ctree

After the roots are closed, root is freed. Yet close_ctree continues
to use it. It works generally because no new memory is allocated in
the interim, but with glibc malloc perturbing enabled, it crashes
every time. This is because root->fs_info points to garbage.

This patch uses the already-cached fs_info variable for the rest of
the accesses and fixes the crash.

This issue was reported at:
https://bugzilla.novell.com/show_bug.cgi?id=603620

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

diff --git a/disk-io.c b/disk-io.c
index c1ed8c8..a6e1000 100644 (file)
--- a/disk-io.c
+++ b/disk-io.c
@@ -970,13 +970,13 @@ int close_ctree(struct btrfs_root *root)
        if (fs_info->csum_root->node)
                free_extent_buffer(fs_info->csum_root->node);
 
-       if (root->fs_info->log_root_tree) {
-               if (root->fs_info->log_root_tree->node)
-                       free_extent_buffer(root->fs_info->log_root_tree->node);
-               free(root->fs_info->log_root_tree);
+       if (fs_info->log_root_tree) {
+               if (fs_info->log_root_tree->node)
+                       free_extent_buffer(fs_info->log_root_tree->node);
+               free(fs_info->log_root_tree);
        }
 
-       close_all_devices(root->fs_info);
+       close_all_devices(fs_info);
        extent_io_tree_cleanup(&fs_info->extent_cache);
        extent_io_tree_cleanup(&fs_info->free_space_cache);
        extent_io_tree_cleanup(&fs_info->block_group_cache);