dm ioctl: prevent empty message

Detect invalid empty messages in core dm instead of requiring every target to
check this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 4cacdad2270a..1622a6bc0bfd 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1402,6 +1402,11 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
                 goto out;
         }
 
+        if (!argc) {
+                DMWARN("Empty message received.");
+                goto out;
+        }
+
         table = dm_get_live_table(md);
         if (!table)
                 goto out_argv;