[PATCH v2] Btrfs: fix use after free when close_ctree frees the orphan_rsv

[Chris Mason <clm@fb.com>]

>From 471717f48f9d853a6ced290d91e8b7f1d1c039da Mon Sep 17 00:00:00 2001
From: Chris Mason <clm@fb.com>
Date: Mon, 6 Apr 2015 18:17:00 -0700
Subject: [PATCH] Btrfs: fix use after free when close_ctree frees the
 orphan_rsv

Near the end of close_ctree, we're calling btrfs_free_block_rsv
to free up the orphan rsv.  The problem is this call updates the
space_info, which has already been freed.

This adds a new __ function that directly calls kfree instead of trying
to update the space infos.

Signed-off-by: Chris Mason <clm@fb.com>
---

 v1 -> v2: whoops, get __btrfs-free_block_rsv in the right commit

 fs/btrfs/ctree.h       | 1 +
 fs/btrfs/disk-io.c     | 2 +-
 fs/btrfs/extent-tree.c | 7 +++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e1800d4..21032ed 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3488,6 +3488,7 @@ struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_root *root,
 					      unsigned short type);
 void btrfs_free_block_rsv(struct btrfs_root *root,
 			  struct btrfs_block_rsv *rsv);
+void __btrfs_free_block_rsv(struct btrfs_block_rsv *rsv);
 int btrfs_block_rsv_add(struct btrfs_root *root,
 			struct btrfs_block_rsv *block_rsv, u64 num_bytes,
 			enum btrfs_reserve_flush_enum flush);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index bb589b5..a123626 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3746,7 +3746,7 @@ void close_ctree(struct btrfs_root *root)
 
 	btrfs_free_stripe_hash_table(fs_info);
 
-	btrfs_free_block_rsv(root, root->orphan_block_rsv);
+	__btrfs_free_block_rsv(root->orphan_block_rsv);
 	root->orphan_block_rsv = NULL;
 
 	lock_chunks(root);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9a53afc..0f1be4a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4925,6 +4925,13 @@ void btrfs_free_block_rsv(struct btrfs_root *root,
 	kfree(rsv);
 }
 
+void __btrfs_free_block_rsv(struct btrfs_block_rsv *rsv)
+{
+	if (!rsv)
+		return;
+	kfree(rsv);
+}
+
 int btrfs_block_rsv_add(struct btrfs_root *root,
 			struct btrfs_block_rsv *block_rsv, u64 num_bytes,
 			enum btrfs_reserve_flush_enum flush)
-- 
1.8.1