linux-kernel - [PATCH 4.4 29/41] btrfs: prevent to set invalid default subvolid

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Message-Id: <20171003114221.676994983@linuxfoundation.org>
Date:   Tue,  3 Oct 2017 14:21:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Satoru Takeuchi <satoru.takeuchi@...il.com>,
        Qu Wenruo <quwenruo.btrfs@....com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 4.4 29/41] btrfs: prevent to set invalid default subvolid

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: satoru takeuchi <satoru.takeuchi@...il.com>

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@...il.com>
Reviewed-by: Qu Wenruo <quwenruo.btrfs@....com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/ioctl.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4118,6 +4118,10 @@ static long btrfs_ioctl_default_subvol(s
 		ret = PTR_ERR(new_root);
 		goto out;
 	}
+	if (!is_fstree(new_root->objectid)) {
+		ret = -ENOENT;
+		goto out;
+	}
 
 	path = btrfs_alloc_path();
 	if (!path) {