From 2971585b27f6a810c50b6f3a9ac391aa4d13fdf5 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 11 Apr 2018 15:23:56 -0400 Subject: random: set up the NUMA crng instances after the CRNG is fully initialized commit 8ef35c866f8862df074a49a93b0309725812dea8 upstream. Until the primary_crng is fully initialized, don't initialize the NUMA crng nodes. Otherwise users of /dev/urandom on NUMA systems before the CRNG is fully initialized can get very bad quality randomness. Of course everyone should move to getrandom(2) where this won't be an issue, but there's a lot of legacy code out there. This related to CVE-2018-1108. Reported-by: Jann Horn Fixes: 1e7f583af67b ("random: make /dev/urandom scalable for silly...") Cc: stable@kernel.org # 4.8+ Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 46 +++++++++++++++++++++++++++------------------- 1 file changed, 27 insertions(+), 19 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/random.c b/drivers/char/random.c index 8d08a8062904..b979173cb0e1 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -819,6 +819,32 @@ static int crng_fast_load(const char *cp, size_t len) return 1; } +#ifdef CONFIG_NUMA +static void numa_crng_init(void) +{ + int i; + struct crng_state *crng; + struct crng_state **pool; + + pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL); + for_each_online_node(i) { + crng = kmalloc_node(sizeof(struct crng_state), + GFP_KERNEL | __GFP_NOFAIL, i); + spin_lock_init(&crng->lock); + crng_initialize(crng); + pool[i] = crng; + } + mb(); + if (cmpxchg(&crng_node_pool, NULL, pool)) { + for_each_node(i) + kfree(pool[i]); + kfree(pool); + } +} +#else +static void numa_crng_init(void) {} +#endif + static void crng_reseed(struct crng_state *crng, struct entropy_store *r) { unsigned long flags; @@ -848,6 +874,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r) memzero_explicit(&buf, sizeof(buf)); crng->init_time = jiffies; if (crng == &primary_crng && crng_init < 2) { + numa_crng_init(); crng_init = 2; process_random_ready_list(); wake_up_interruptible(&crng_init_wait); @@ -1661,29 +1688,10 @@ static void init_std_data(struct entropy_store *r) */ static int rand_initialize(void) { -#ifdef CONFIG_NUMA - int i; - struct crng_state *crng; - struct crng_state **pool; -#endif - init_std_data(&input_pool); init_std_data(&blocking_pool); crng_initialize(&primary_crng); crng_global_init_time = jiffies; - -#ifdef CONFIG_NUMA - pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL); - for_each_online_node(i) { - crng = kmalloc_node(sizeof(struct crng_state), - GFP_KERNEL | __GFP_NOFAIL, i); - spin_lock_init(&crng->lock); - crng_initialize(crng); - pool[i] = crng; - } - mb(); - crng_node_pool = pool; -#endif return 0; } early_initcall(rand_initialize); -- cgit v1.2.3