From 5744a0927df22f46e4b7f134b3dfb405fdfcf6ce Mon Sep 17 00:00:00 2001 From: Jeremy Cline Date: Wed, 2 May 2018 15:16:29 -0400 Subject: [PATCH 1/2] Revert "random: use a different mixing algorithm for add_device_randomness()" This reverts commit 89b59f050347d376c2ace8b1ceb908a218cfdc2e. Signed-off-by: Jeremy Cline --- drivers/char/random.c | 55 ++++--------------------------------------- 1 file changed, 4 insertions(+), 51 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 8f4e11842c60..aa5b04af86c6 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -831,10 +831,6 @@ static void numa_crng_init(void) 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. - */ static int crng_fast_load(const char *cp, size_t len) { unsigned long flags; @@ -861,51 +857,6 @@ static int crng_fast_load(const char *cp, size_t len) return 1; } -/* - * crng_slow_load() is called by add_device_randomness, which has two - * attributes. (1) We can't trust the buffer passed to it is - * guaranteed to be unpredictable (so it might not have any entropy at - * all), and (2) it doesn't have the performance constraints of - * crng_fast_load(). - * - * So we do something more comprehensive which is guaranteed to touch - * all of the primary_crng's state, and which uses a LFSR with a - * period of 255 as part of the mixing algorithm. Finally, we do - * *not* advance crng_init_cnt since buffer we may get may be something - * like a fixed DMI table (for example), which might very well be - * unique to the machine, but is otherwise unvarying. - */ -static int crng_slow_load(const char *cp, size_t len) -{ - unsigned long flags; - static unsigned char lfsr = 1; - unsigned char tmp; - unsigned i, max = CHACHA20_KEY_SIZE; - const char * src_buf = cp; - char * dest_buf = (char *) &primary_crng.state[4]; - - if (!spin_trylock_irqsave(&primary_crng.lock, flags)) - return 0; - if (crng_init != 0) { - spin_unlock_irqrestore(&primary_crng.lock, flags); - return 0; - } - if (len > max) - max = len; - - for (i = 0; i < max ; i++) { - tmp = lfsr; - lfsr >>= 1; - if (tmp & 1) - lfsr ^= 0xE1; - tmp = dest_buf[i % CHACHA20_KEY_SIZE]; - dest_buf[i % CHACHA20_KEY_SIZE] ^= src_buf[i % len] ^ lfsr; - lfsr += (tmp << 3) | (tmp >> 5); - } - spin_unlock_irqrestore(&primary_crng.lock, flags); - return 1; -} - static void crng_reseed(struct crng_state *crng, struct entropy_store *r) { unsigned long flags; @@ -1089,8 +1040,10 @@ void add_device_randomness(const void *buf, unsigned int size) unsigned long time = random_get_entropy() ^ jiffies; unsigned long flags; - if (!crng_ready() && size) - crng_slow_load(buf, size); + if (!crng_ready()) { + crng_fast_load(buf, size); + return; + } trace_add_device_randomness(size, _RET_IP_); spin_lock_irqsave(&input_pool.lock, flags); -- 2.17.0 From e1b1b5b62740b0e6ea8258a4eb81b2a336538fed Mon Sep 17 00:00:00 2001 From: Jeremy Cline Date: Wed, 2 May 2018 15:18:03 -0400 Subject: [PATCH 2/2] Revert "random: fix crng_ready() test" This reverts commit cd8d7a5778a4abf76ee8fe8f1bfcf78976029f8d. Signed-off-by: Jeremy Cline --- drivers/char/random.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index aa5b04af86c6..ef05cc685b74 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -428,7 +428,7 @@ struct crng_state primary_crng = { * its value (from 0->1->2). */ static int crng_init = 0; -#define crng_ready() (likely(crng_init > 1)) +#define crng_ready() (likely(crng_init > 0)) static int crng_init_cnt = 0; static unsigned long crng_global_init_time = 0; #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE) @@ -838,7 +838,7 @@ static int crng_fast_load(const char *cp, size_t len) if (!spin_trylock_irqsave(&primary_crng.lock, flags)) return 0; - if (crng_init != 0) { + if (crng_ready()) { spin_unlock_irqrestore(&primary_crng.lock, flags); return 0; } @@ -913,7 +913,7 @@ static void _extract_crng(struct crng_state *crng, { unsigned long v, flags; - if (crng_ready() && + if (crng_init > 1 && (time_after(crng_global_init_time, crng->init_time) || time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))) crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL); @@ -1200,7 +1200,7 @@ void add_interrupt_randomness(int irq, int irq_flags) fast_mix(fast_pool); add_interrupt_bench(cycles); - if (unlikely(crng_init == 0)) { + if (!crng_ready()) { if ((fast_pool->count >= 64) && crng_fast_load((char *) fast_pool->pool, sizeof(fast_pool->pool))) { @@ -2269,7 +2269,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, { struct entropy_store *poolp = &input_pool; - if (unlikely(crng_init == 0)) { + if (!crng_ready()) { crng_fast_load(buffer, count); return; } -- 2.17.0