btrfs: scrub: reject unsupported scrub flags

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>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ba769a1eb87ab24e535576b37db26e50be58b02b..25833b4eeaf574ea28c44f2be2dae38627b19ee8 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3161,6 +3161,11 @@ 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 ada0a489bf2b69287416321e7dcf43144de68a0b..dbb8b96da50d3088489c3055f58ac992cb3b3ba9 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 */