linux-kernel - [PATCH 3.10 132/139] btrfs: prevent to set invalid default subvolid

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Message-Id: <1509571624-5001-33-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:26:57 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     satoru takeuchi <satoru.takeuchi@...il.com>,
        David Sterba <dsterba@...e.com>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 132/139] btrfs: prevent to set invalid default subvolid

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")
Cc: <stable@...r.kernel.org>
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: Willy Tarreau <w@....eu>
---
 fs/btrfs/ioctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 296cc1b..7831e68 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2974,6 +2974,10 @@ 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;
+	}
 
 	if (btrfs_root_refs(&new_root->root_item) == 0) {
 		ret = -ENOENT;
-- 
2.8.0.rc2.1.gbe9624a