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 fe2fb81da46ba21bec5cafeb01300f6623f92ca1..0cebc203c4cccbdab903a2a5c25a5b26f8f57fa6 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4050,6 +4050,11 @@ 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 5655e89b962be87e5bd6cb1710669cbffad676a0..d4d4fa0bb362e6ae3f1e4e46694080c7f8e6126f 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -181,6 +181,7 @@ 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 */