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From: "Tobin C. Harding" <me@tobin.cc>
To: linux-kernel@vger.kernel.org
Cc: "Tobin C. Harding" <me@tobin.cc>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Kees Cook <keescook@chromium.org>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH v2 3/4] vsprintf: Use hw RNG for ptr_key
Date: Thu,  3 May 2018 08:50:25 +1000	[thread overview]
Message-ID: <1525301426-23543-4-git-send-email-me@tobin.cc> (raw)
In-Reply-To: <1525301426-23543-1-git-send-email-me@tobin.cc>

Currently we must wait for enough entropy to become available before
hashed pointers can be printed.  We can remove this wait by using the
hw RNG if available.

Use hw RNG to get keying material by default if available.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 lib/vsprintf.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b82f0c6c2aec..3697a19c2b25 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1657,9 +1657,8 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
 static bool have_filled_random_ptr_key __read_mostly;
 static siphash_key_t ptr_key __read_mostly;
 
-static void fill_random_ptr_key(struct random_ready_callback *unused)
+static void ptr_key_ready(void)
 {
-	get_random_bytes(&ptr_key, sizeof(ptr_key));
 	/*
 	 * have_filled_random_ptr_key==true is dependent on get_random_bytes().
 	 * ptr_to_id() needs to see have_filled_random_ptr_key==true
@@ -1669,14 +1668,28 @@ static void fill_random_ptr_key(struct random_ready_callback *unused)
 	WRITE_ONCE(have_filled_random_ptr_key, true);
 }
 
+static void fill_random_ptr_key(struct random_ready_callback *unused)
+{
+	get_random_bytes(&ptr_key, sizeof(ptr_key));
+	ptr_key_ready();
+}
+
 static struct random_ready_callback random_ready = {
 	.func = fill_random_ptr_key
 };
 
 static int __init initialize_ptr_random(void)
 {
-	int ret = add_random_ready_callback(&random_ready);
+	int ret;
+	int key_size = sizeof(ptr_key);
+
+	/* Use hw RNG if available */
+	if (get_random_bytes_arch(&ptr_key, key_size) == key_size) {
+		ptr_key_ready();
+		return 0;
+	}
 
+	ret = add_random_ready_callback(&random_ready);
 	if (!ret) {
 		return 0;
 	} else if (ret == -EALREADY) {
-- 
2.7.4

  parent reply	other threads:[~2018-05-02 22:50 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-02 22:50 [PATCH v2 0/4] enable early printing of hashed pointers Tobin C. Harding
2018-05-02 22:50 ` [PATCH v2 1/4] random: Fix whitespace pre random-bytes work Tobin C. Harding
2018-05-02 22:50 ` [PATCH v2 2/4] random: Return nbytes filled from hw RNG Tobin C. Harding
2018-05-02 22:50 ` Tobin C. Harding [this message]
2018-05-02 22:50 ` [PATCH v2 4/4] vsprintf: Add command line option debug_early_boot Tobin C. Harding
2018-05-03  4:57   ` Kees Cook
2018-05-03  5:09     ` Tobin C. Harding

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