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-Tag: archive/raspbian/4.9.51-1+rpi1~5^2~12
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=b081819d2c6b53245ee13d7d95e730da3e7938b9;p=linux-4.9.git

btrfs: prevent to set invalid default subvolid

commit 6d6d282932d1a609e60dc4467677e0e863682f57 upstream.

`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")
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 90185e94d79d..0fe346c4bd28 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4082,6 +4082,10 @@ 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) {