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>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 01a260f..23cab7a 100644 (file)
--- 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 df58a41..052481f 100644 (file)
--- 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();