From ee7998c50c2697737c6530431709f77c852bf0d6 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 12 Jul 2017 14:34:04 -0700
Subject: [PATCH] random: do not ignore early device randomness
The add_device_randomness() function would ignore incoming bytes if the
crng wasn't ready. This additionally makes sure to make an early enough
call to add_latent_entropy() to influence the initial stack canary,
which is especially important on non-x86 systems where it stays the same
through the life of the boot.
Link: http://lkml.kernel.org/r/20170626233038.GA48751@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jessica Yu <jeyu@redhat.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/char/random.c | 5 +++++
init/main.c | 1 +
2 files changed, 6 insertions(+)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 01a260f674374..23cab7a8c1c19 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -987,6 +987,11 @@ void add_device_randomness(const void *buf, unsigned int size)
unsigned long time = random_get_entropy() ^ jiffies;
unsigned long flags;
+ if (!crng_ready()) {
+ crng_fast_load(buf, size);
+ return;
+ }
+
trace_add_device_randomness(size, _RET_IP_);
spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(&input_pool, buf, size);
diff --git a/init/main.c b/init/main.c
index df58a416dd1da..052481fbe3633 100644
--- a/init/main.c
+++ b/init/main.c
@@ -518,6 +518,7 @@ asmlinkage __visible void __init start_kernel(void)
/*
* Set up the initial canary ASAP:
*/
+ add_latent_entropy();
boot_init_stack_canary();
cgroup_init_early();
--
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