[PATCH] mmc: block: reject invalid perdev_minors before division

From: Xu Rao <[email protected]>

The mmcblk.perdev_minors module parameter is parsed as a signed int and
is used during mmc_blk_init() to compute the number of supported block
devices.

Passing perdev_minors=0 makes the init path divide by zero when it
computes max_devices. Negative values are invalid as well and would make
max_devices negative before it is later used as an IDA limit.

Reject non-positive perdev_minors values before registering any mmcblk
resources.

Signed-off-by: Xu Rao <[email protected]>
---
 drivers/mmc/core/block.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 0274e8d07660..9cfd27c90215 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -3338,6 +3338,11 @@ static int __init mmc_blk_init(void)
 {
 	int res;
 
+	if (perdev_minors <= 0) {
+		pr_err("mmcblk: invalid minors per device: %d\n", perdev_minors);
+		return -EINVAL;
+	}
+
 	res  = bus_register(&mmc_rpmb_bus_type);
 	if (res < 0) {
 		pr_err("mmcblk: could not register RPMB bus type\n");
-- 
2.50.1