[PATCH for 4.3] btrfs: check unsupported filters in balance arguments

[David Sterba <dsterba@suse.com>]

We don't verify that all the balance filter arguments supplemented by
the flags are actually known to the kernel. Thus we let it silently pass
and do nothing.

At the moment this means only the 'limit' filter, but we're going to add
a few more soon so it's better to have that fixed. Also in older stable
kernels so that it works with newer userspace tools.

Cc: stable@vger.kernel.org # 3.16+
Signed-off-by: David Sterba <dsterba@suse.com>
---

Please try to get it into 4.3, before the new balance filters (stripes,
enhanced 'limit') get merged. This would cause us headaches when we would not
have the kernel checks and try to run updated btrfs-progs against that.

 fs/btrfs/ioctl.c   | 5 +++++
 fs/btrfs/volumes.h | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0adf5422fce9..3e3e6130637f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4639,6 +4639,11 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
 		bctl->flags |= BTRFS_BALANCE_TYPE_MASK;
 	}
 
+	if (bctl->flags & ~(BTRFS_BALANCE_ARGS_MASK | BTRFS_BALANCE_TYPE_MASK)) {
+		ret = -EINVAL;
+		goto out_bargs;
+	}
+
 do_balance:
 	/*
 	 * Ownership of bctl and mutually_exclusive_operation_running
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2ca784a14e84..595279a8b99f 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -376,6 +376,14 @@ struct map_lookup {
 #define BTRFS_BALANCE_ARGS_VRANGE	(1ULL << 4)
 #define BTRFS_BALANCE_ARGS_LIMIT	(1ULL << 5)
 
+#define BTRFS_BALANCE_ARGS_MASK			\
+	(BTRFS_BALANCE_ARGS_PROFILES |		\
+	 BTRFS_BALANCE_ARGS_USAGE |		\
+	 BTRFS_BALANCE_ARGS_DEVID | 		\
+	 BTRFS_BALANCE_ARGS_DRANGE |		\
+	 BTRFS_BALANCE_ARGS_VRANGE |		\
+	 BTRFS_BALANCE_ARGS_LIMIT)
+
 /*
  * Profile changing flags.  When SOFT is set we won't relocate chunk if
  * it already has the target profile (even though it may be
-- 
2.1.3