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 4cacdad..1622a6b 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;