RDMA/bnxt_re: Fix buffer overflow in debugfs code

Add some bounds checking to prevent memory corruption in
bnxt_re_cc_config_set().  This is debugfs code so the bug can only be
triggered by root.

Fixes: 656dff55da ("RDMA/bnxt_re: Congestion control settings using debugfs hook")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/a6b081ab-55fe-4d0c-8f69-c5e5a59e9141@stanley.mountain
Acked-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/bnxt_re/debugfs.c

@@ -285,6 +285,9 @@ static ssize_t bnxt_re_cc_config_set(struct file *filp, const char __user *buffe
 	u32 val;
 	int rc;
 
+	if (count >= sizeof(buf))
+		return -EINVAL;
+
 	if (copy_from_user(buf, buffer, count))
 		return -EFAULT;