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random: set up the NUMA crng instances after the CRNG is fully initialized

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commit 8ef35c866f 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 <jannh@google.com>
Fixes: 1e7f583af6 ("random: make /dev/urandom scalable for silly...")
Cc: stable@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Theodore Ts'o
2018-04-11 15:23:56 -04:00
committed by Greg Kroah-Hartman
parent 0467c15b09
commit 13eec12cfa
1 changed files with 27 additions and 0 deletions
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27
drivers/char/random.c
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@@ -799,6 +799,32 @@ static void crng_initialize(struct crng_state *crng)
crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 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
/*
* crng_fast_load() can be called by code in the interrupt service
* path. So we can't afford to dilly-dally.
@@ -957,6 +983,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
if (crng == &primary_crng && crng_init < 2) {
numa_crng_init();
invalidate_batched_entropy();
numa_crng_init();
crng_init = 2;
process_random_ready_list();
wake_up_interruptible(&crng_init_wait);