[PATCH 3/3] null_blk: validated the number of devices

["André Almeida" <andrealmeid@collabora.com>]

There is no sense defining a negative number of devices, so change the type
to unsigned. If the number of devices is 0, it is impossible to the
userspace interact with the module, so there is no reasoning in loading
it.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
---
 drivers/block/null_blk_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 7bc553ff7407..ab4b87677139 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -141,7 +141,7 @@ static int g_bs = 512;
 module_param_named(bs, g_bs, int, 0444);
 MODULE_PARM_DESC(bs, "Block size (in bytes)");
 
-static int nr_devices = 1;
+static unsigned int nr_devices = 1;
 module_param(nr_devices, int, 0444);
 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
 
@@ -1758,6 +1758,10 @@ static int __init null_init(void)
 		pr_err("null_blk: legacy IO path no longer available\n");
 		return -EINVAL;
 	}
+	if (!nr_devices) {
+		pr_err("null_blk: invalid number of devices\n");
+		return -EINVAL;
+	}
 	if (g_queue_mode == NULL_Q_MQ && g_use_per_node_hctx) {
 		if (g_submit_queues != nr_online_nodes) {
 			pr_warn("null_blk: submit_queues param is set to %u.\n",
-- 
2.23.0