btrfs: scrub: reject unsupported scrub flags

commit 604e6681e114d05a2e384c4d1e8ef81918037ef5 upstream.

Since the introduction of scrub interface, the only flag that we support
is BTRFS_SCRUB_READONLY.  Thus there is no sanity checks, if there are
some undefined flags passed in, we just ignore them.

This is problematic if we want to introduce new scrub flags, as we have
no way to determine if such flags are supported.

Address the problem by introducing a check for the flags, and if
unsupported flags are set, return -EOPNOTSUPP to inform the user space.

This check should be backported for all supported kernels before any new
scrub flags are introduced.

CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.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 c232636ecdfeae096e2c3bd91ab9bec701a113c5..bff2d1fd3c812d3427502ecd567e21ced29c9ec8 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3160,6 +3160,11 @@ static long btrfs_ioctl_scrub(struct file *file, void __user *arg)
        if (IS_ERR(sa))
                return PTR_ERR(sa);
 
+       if (sa->flags & ~BTRFS_SCRUB_SUPPORTED_FLAGS) {
+               ret = -EOPNOTSUPP;
+               goto out;
+       }
+
        if (!(sa->flags & BTRFS_SCRUB_READONLY)) {
                ret = mnt_want_write_file(file);
                if (ret)

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index b4f0f9531119f2df1b9eb4f84ce3e5e19485822a..5864d2d9b79a35029eccebf81d92a1dede948f3a 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -187,6 +187,7 @@ struct btrfs_scrub_progress {
 };
 
 #define BTRFS_SCRUB_READONLY   1
+#define BTRFS_SCRUB_SUPPORTED_FLAGS    (BTRFS_SCRUB_READONLY)
 struct btrfs_ioctl_scrub_args {
        __u64 devid;                            /* in */
        __u64 start;                            /* in */