Commit fe6f1a6a authored Apr 19, 2019 by Jon DeVree Committed by Theodore Ts'o Apr 19, 2019

random: fix CRNG initialization when random.trust_cpu=1



When the system boots with random.trust_cpu=1 it doesn't initialize the
per-NUMA CRNGs because it skips the rest of the CRNG startup code. This
means that the code from 1e7f583a ("random: make /dev/urandom scalable
for silly userspace programs") is not used when random.trust_cpu=1.

crash> dmesg | grep random:
[    0.000000] random: get_random_bytes called from start_kernel+0x94/0x530 with crng_init=0
[    0.314029] random: crng done (trusting CPU's manufacturer)
crash> print crng_node_pool
$6 = (struct crng_state **) 0x0

After adding the missing call to numa_crng_init() the per-NUMA CRNGs are
initialized again:

crash> dmesg | grep random:
[    0.000000] random: get_random_bytes called from start_kernel+0x94/0x530 with crng_init=0
[    0.314031] random: crng done (trusting CPU's manufacturer)
crash> print crng_node_pool
$1 = (struct crng_state **) 0xffff9a915f4014a0

The call to invalidate_batched_entropy() was also missing. This is
important for architectures like PPC and S390 which only have the
arch_get_random_seed_* functions.

Fixes: 39a8883a ("random: add a config option to trust the CPU's hwrng")
Signed-off-by: Jon DeVree <nuxi@vault24.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent d5553523

drivers/char/random.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -772,6 +772,7 @@ static struct crng_state **crng_node_pool __read_mostly;
		#endif

		static void invalidate_batched_entropy(void);
		static void numa_crng_init(void);

		static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
		static int __init parse_trust_cpu(char *arg)
		@@ -800,7 +801,9 @@ static void crng_initialize(struct crng_state *crng)
		}
		crng->state[i] ^= rv;
		}
		if (trust_cpu && arch_init) {
		if (trust_cpu && arch_init && crng == &primary_crng) {
		invalidate_batched_entropy();
		numa_crng_init();
		crng_init = 2;
		pr_notice("random: crng done (trusting CPU's manufacturer)\n");
		}

Admin message