From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxx> Cc: "Theodore Ts'o" <tytso@xxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jessica Yu <jeyu@xxxxxxxxxx> Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Lokesh Vutla <lokeshvutla@xxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/char/random.c | 5 +++++ init/main.c | 1 + 2 files changed, 6 insertions(+) diff -puN drivers/char/random.c~random-do-not-ignore-early-device-randomness drivers/char/random.c --- a/drivers/char/random.c~random-do-not-ignore-early-device-randomness +++ a/drivers/char/random.c @@ -987,6 +987,11 @@ void add_device_randomness(const void *b 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 -puN init/main.c~random-do-not-ignore-early-device-randomness init/main.c --- a/init/main.c~random-do-not-ignore-early-device-randomness +++ a/init/main.c @@ -518,6 +518,7 @@ asmlinkage __visible void __init start_k /* * Set up the initial canary ASAP: */ + add_latent_entropy(); boot_init_stack_canary(); cgroup_init_early(); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
