[PATCH v2 4/5] vsprintf: initialize siphash key using notifier

Jason A. Donenfeld
2022-11-18T13:34:37Z

Rather than polling every second, use the new notifier to do this at
exactly the right moment.

Cc: Mike Galbraith <efault@gmx.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
lib/vsprintf.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 24f37bab8bc1..890607b32235 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -41,6 +41,7 @@
#include <linux/siphash.h>
#include <linux/compiler.h>
#include <linux/property.h>
+#include <linux/notifier.h>
#ifdef CONFIG_BLOCK
#include <linux/blkdev.h>
#endif
@@ -752,26 +753,21 @@ early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);

static bool filled_random_ptr_key __read_mostly;
static siphash_key_t ptr_key __read_mostly;
-static void fill_ptr_key_workfn(struct work_struct *work);
-static DECLARE_DELAYED_WORK(fill_ptr_key_work, fill_ptr_key_workfn);

-static void fill_ptr_key_workfn(struct work_struct *work)
+static int fill_ptr_key(struct notifier_block *nb, unsigned long action, void *data)
{
- if (!rng_is_initialized()) {
- queue_delayed_work(system_unbound_wq, &fill_ptr_key_work, HZ * 2);
- return;
- }
-
get_random_bytes(&ptr_key, sizeof(ptr_key));

/* Pairs with smp_rmb() before reading ptr_key. */
smp_wmb();
WRITE_ONCE(filled_random_ptr_key, true);
+ return 0;
}

static int __init vsprintf_init_hashval(void)
{
- fill_ptr_key_workfn(NULL);
+ static struct notifier_block fill_ptr_key_nb = { .notifier_call = fill_ptr_key };
+ execute_with_initialized_rng(&fill_ptr_key_nb);
return 0;
}
subsys_initcall(vsprintf_init_hashval)
--
2.38.1