From: satoru takeuchi <satoru.takeuchi@gmail.com>
Date: Tue, 12 Sep 2017 13:42:52 +0000 (+0900)
Subject: btrfs: prevent to set invalid default subvolid
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=6d6d282932d1a609e60dc4467677e0e863682f57;p=openwrt%2Fstaging%2Fblogic.git

btrfs: prevent to set invalid default subvolid

`btrfs sub set-default` succeeds to set an ID which isn't corresponding to any
fs/file tree. If such the bad ID is set to a filesystem, we can't mount this
filesystem without specifying `subvol` or `subvolid` mount options.

Fixes: 6ef5ed0d386b ("Btrfs: add ioctl and incompat flag to set the default mount subvol")
Cc: <stable@vger.kernel.org>
Signed-off-by: Satoru Takeuchi <satoru.takeuchi@gmail.com>
Reviewed-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cf1c2ee030dd..d4a77993e52f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4057,6 +4057,10 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 		ret = PTR_ERR(new_root);
 		goto out;
 	}
+	if (!is_fstree(new_root->objectid)) {
+		ret = -ENOENT;
+		goto out;
+	}
 
 	path = btrfs_alloc_path();
 	if (!path) {