From: Theodore Ts'o Date: Wed, 11 Jun 2014 03:09:20 +0000 (-0400) Subject: random: remove unneeded hash of a portion of the entropy pool X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=85608f8e16c28f818f6bb9918958d231afa8bec2;p=linux-beck.git random: remove unneeded hash of a portion of the entropy pool We previously extracted a portion of the entropy pool in mix_pool_bytes() and hashed it in to avoid racing CPU's from returning duplicate random values. Now that we are using a spinlock to prevent this from happening, this is no longer necessary. So remove it, to simplify the code a bit. Signed-off-by: Theodore Ts'o Cc: George Spelvin --- diff --git a/drivers/char/random.c b/drivers/char/random.c index 922a2e4089f9..bc0de22f31f4 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -481,9 +481,9 @@ static __u32 const twist_table[8] = { * the entropy is concentrated in the low-order bits. */ static void _mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes, __u8 out[64]) + int nbytes) { - unsigned long i, j, tap1, tap2, tap3, tap4, tap5; + unsigned long i, tap1, tap2, tap3, tap4, tap5; int input_rotate; int wordmask = r->poolinfo->poolwords - 1; const char *bytes = in; @@ -525,27 +525,23 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in, r->input_rotate = input_rotate; r->add_ptr = i; - - if (out) - for (j = 0; j < 16; j++) - ((__u32 *)out)[j] = r->pool[(i - j) & wordmask]; } static void __mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes, __u8 out[64]) + int nbytes) { trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_); - _mix_pool_bytes(r, in, nbytes, out); + _mix_pool_bytes(r, in, nbytes); } static void mix_pool_bytes(struct entropy_store *r, const void *in, - int nbytes, __u8 out[64]) + int nbytes) { unsigned long flags; trace_mix_pool_bytes(r->name, nbytes, _RET_IP_); spin_lock_irqsave(&r->lock, flags); - _mix_pool_bytes(r, in, nbytes, out); + _mix_pool_bytes(r, in, nbytes); spin_unlock_irqrestore(&r->lock, flags); } @@ -737,13 +733,13 @@ void add_device_randomness(const void *buf, unsigned int size) trace_add_device_randomness(size, _RET_IP_); spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(&input_pool, buf, size, NULL); - _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); + _mix_pool_bytes(&input_pool, buf, size); + _mix_pool_bytes(&input_pool, &time, sizeof(time)); spin_unlock_irqrestore(&input_pool.lock, flags); spin_lock_irqsave(&nonblocking_pool.lock, flags); - _mix_pool_bytes(&nonblocking_pool, buf, size, NULL); - _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); + _mix_pool_bytes(&nonblocking_pool, buf, size); + _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time)); spin_unlock_irqrestore(&nonblocking_pool.lock, flags); } EXPORT_SYMBOL(add_device_randomness); @@ -776,7 +772,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) sample.cycles = random_get_entropy(); sample.num = num; r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; - mix_pool_bytes(r, &sample, sizeof(sample), NULL); + mix_pool_bytes(r, &sample, sizeof(sample)); /* * Calculate number of bits of randomness we probably added. @@ -864,7 +860,7 @@ void add_interrupt_randomness(int irq, int irq_flags) return; } fast_pool->last = now; - __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL); + __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool)); /* * If we have architectural seed generator, produce a seed and @@ -872,7 +868,7 @@ void add_interrupt_randomness(int irq, int irq_flags) * 50% entropic. */ if (arch_get_random_seed_long(&seed)) { - __mix_pool_bytes(r, &seed, sizeof(seed), NULL); + __mix_pool_bytes(r, &seed, sizeof(seed)); credit += sizeof(seed) * 4; } spin_unlock(&r->lock); @@ -955,7 +951,7 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes) ENTROPY_BITS(r), ENTROPY_BITS(r->pull)); bytes = extract_entropy(r->pull, tmp, bytes, random_read_wakeup_bits / 8, rsvd_bytes); - mix_pool_bytes(r, tmp, bytes, NULL); + mix_pool_bytes(r, tmp, bytes); credit_entropy_bits(r, bytes*8); } @@ -1031,7 +1027,6 @@ static void extract_buf(struct entropy_store *r, __u8 *out) unsigned long l[LONGS(20)]; } hash; __u32 workspace[SHA_WORKSPACE_WORDS]; - __u8 extract[64]; unsigned long flags; /* @@ -1060,15 +1055,9 @@ static void extract_buf(struct entropy_store *r, __u8 *out) * brute-forcing the feedback as hard as brute-forcing the * hash. */ - __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract); + __mix_pool_bytes(r, hash.w, sizeof(hash.w)); spin_unlock_irqrestore(&r->lock, flags); - /* - * To avoid duplicates, we atomically extract a portion of the - * pool while mixing, and hash one final time. - */ - sha_transform(hash.w, extract, workspace); - memset(extract, 0, sizeof(extract)); memset(workspace, 0, sizeof(workspace)); /* @@ -1255,14 +1244,14 @@ static void init_std_data(struct entropy_store *r) unsigned long rv; r->last_pulled = jiffies; - mix_pool_bytes(r, &now, sizeof(now), NULL); + mix_pool_bytes(r, &now, sizeof(now)); for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) { if (!arch_get_random_seed_long(&rv) && !arch_get_random_long(&rv)) rv = random_get_entropy(); - mix_pool_bytes(r, &rv, sizeof(rv), NULL); + mix_pool_bytes(r, &rv, sizeof(rv)); } - mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); + mix_pool_bytes(r, utsname(), sizeof(*(utsname()))); } /* @@ -1325,7 +1314,7 @@ static int arch_random_refill(void) if (n) { unsigned int rand_bytes = n * sizeof(unsigned long); - mix_pool_bytes(&input_pool, buf, rand_bytes, NULL); + mix_pool_bytes(&input_pool, buf, rand_bytes); credit_entropy_bits(&input_pool, rand_bytes*4); } @@ -1415,7 +1404,7 @@ write_pool(struct entropy_store *r, const char __user *buffer, size_t count) count -= bytes; p += bytes; - mix_pool_bytes(r, buf, bytes, NULL); + mix_pool_bytes(r, buf, bytes); cond_resched(); }