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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 <tytso@mit.edu>
Cc: George Spelvin <linux@horizon.com>
This commit is contained in:
Theodore Ts'o 2014-06-10 23:09:20 -04:00
parent 91fcb532ef
commit 85608f8e16
1 changed files with 20 additions and 31 deletions
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51
drivers/char/random.c
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@ -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();
}