linux-kernel - [PATCH 9/9] random: group sysctl functions

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Date:   Fri, 11 Feb 2022 13:35:46 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, linux@...inikbrodowski.net
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>
Subject: [PATCH 9/9] random: group sysctl functions

This pulls all of the sysctl-focused functions into the sixth labeled
section.

No functional changes.

Cc: Theodore Ts'o <tytso@....edu>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/char/random.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index a4229474d7fa..bff77654910c 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1537,7 +1537,25 @@ const struct file_operations urandom_fops = {
 
 /********************************************************************
  *
- * Sysctl interface
+ * Sysctl interface.
+ *
+ * These are mostly unused legacy knobs with dummy values to not break
+ * userspace. Still in use, however, are:
+ *
+ * - /proc/sys/kernel/random/boot_id - a UUID representing the current
+ *   boot.
+ *
+ * - /proc/sys/kernel/random/uuid - a random UUID, fresh each time.
+ *
+ * - /proc/sys/kernel/random/poolsize - the total amount of entropy
+ *   that the input pool can hold.
+ *
+ * - /proc/sys/kernel/random/write_wakeup_threshold - the amount of
+ *   entropy in the input pool below which write polls to
+ *   /dev/random will unblock, requesting more entropy. This is
+ *   currently the same value as the previous "poolsize" sysctl. It
+ *   is writable to avoid breaking old userspaces, but writing to it
+ *   does not change any behavior of the RNG.
  *
  ********************************************************************/
 
@@ -1545,8 +1563,8 @@ const struct file_operations urandom_fops = {
 
 #include <linux/sysctl.h>
 
-static int random_min_urandom_seed = 60;
-static int random_write_wakeup_bits = POOL_MIN_BITS;
+static int sysctl_random_min_urandom_seed = 60;
+static int sysctl_random_write_wakeup_bits = POOL_MIN_BITS;
 static int sysctl_poolsize = POOL_BITS;
 static char sysctl_bootid[16];
 
@@ -1603,14 +1621,14 @@ static struct ctl_table random_table[] = {
 	},
 	{
 		.procname	= "write_wakeup_threshold",
-		.data		= &random_write_wakeup_bits,
+		.data		= &sysctl_random_write_wakeup_bits,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
 	{
 		.procname	= "urandom_min_reseed_secs",
-		.data		= &random_min_urandom_seed,
+		.data		= &sysctl_random_min_urandom_seed,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
@@ -1641,4 +1659,4 @@ static int __init random_sysctls_init(void)
 	return 0;
 }
 device_initcall(random_sysctls_init);
-#endif	/* CONFIG_SYSCTL */
+#endif
-- 
2.35.0