From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 24 Jan 2020 09:32:28 -0500
Git-commit: 9326f76f4bc4f4fc624d2f5263386ac879957867
Patch-mainline: 5.7-rc1
References: bsc#1176019
Subject: [PATCH] btrfs: hold a ref on the root in resolve_indirect_ref

We're looking up a random root, we need to hold a ref on it while we're
using it.

Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/backref.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index e5d85311d5d5..193747b6e1f9 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -524,7 +524,13 @@ static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 	if (IS_ERR(root)) {
 		srcu_read_unlock(&fs_info->subvol_srcu, index);
 		ret = PTR_ERR(root);
-		goto out;
+		goto out_free;
+	}
+
+	if (!btrfs_grab_fs_root(root)) {
+		srcu_read_unlock(&fs_info->subvol_srcu, index);
+		ret = -ENOENT;
+		goto out_free;
 	}
 
 	if (btrfs_is_testing(fs_info)) {
@@ -577,6 +583,8 @@ static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 	ret = add_all_parents(root, path, parents, ref, level, time_seq,
 			      extent_item_pos, total_refs, ignore_offset);
 out:
+	btrfs_put_fs_root(root);
+out_free:
 	path->lowest_level = 0;
 	btrfs_release_path(path);
 	return ret;
-- 
2.26.2