Commit ee7998c5 authored Jul 12, 2017 by Kees Cook Committed by Linus Torvalds Jul 12, 2017

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>

parent 9380fa60

drivers/char/random.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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);

init/main.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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();

Admin message