[PATCH v3 2/6] printk: add bounds checking to boot_delay

[Andrew Murray <amurray@thegoodpenguin.co.uk>]

As the boot_delay kernel parameter represents a duration in
milliseconds, let's set its type to be unsigned int and add
bounds checking.

Please note that the existing pr_debug will only be displayed
when boot_delay is non-zero:

 pr_debug("printk_delay: %u, preset_lpj: %ld, lpj: %lu, "
          "HZ: %d, loops_per_msec: %llu\n",
          printk_delay_msec, preset_lpj, lpj, HZ, loops_per_msec);

Signed-off-by: Andrew Murray <amurray@thegoodpenguin.co.uk>
---
 kernel/printk/printk.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 31aabdf8248cc39c54ee11685d4a37deac1c174c..8be562c9be277670ba3209ed1f810fc87175848a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1291,19 +1291,22 @@ static bool suppress_message_printing(int level)
 
 #ifdef CONFIG_BOOT_PRINTK_DELAY
 
-static int boot_delay; /* msecs delay after each printk during bootup */
+static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 static unsigned long long loops_per_msec;	/* based on boot_delay */
 
 static int __init boot_delay_setup(char *str)
 {
 	unsigned long lpj;
+	int boot_delay_val;
 
 	lpj = preset_lpj ? preset_lpj : 1000000;	/* some guess */
 	loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 
-	get_option(&str, &boot_delay);
-	if (boot_delay > 10 * 1000)
-		boot_delay = 0;
+	get_option(&str, &boot_delay_val);
+	if (boot_delay_val < 0 || boot_delay_val > 10 * 1000)
+		return 0;
+
+	boot_delay = (unsigned int)boot_delay_val;
 
 	pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 		"HZ: %d, loops_per_msec: %llu\n",

-- 
2.34.1