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Message-Id: <1402730118-23122-2-git-send-email-tytso@mit.edu>
Date: Sat, 14 Jun 2014 03:15:16 -0400
From: Theodore Ts'o <tytso@....edu>
To: Linux Kernel Developers List <linux-kernel@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>, George Spelvin <linux@...izon.com>
Subject: [PATCH-v2 2/4] 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@....edu>
Cc: George Spelvin <linux@...izon.com>
---
drivers/char/random.c | 51 ++++++++++++++++++++-------------------------------
1 file changed, 20 insertions(+), 31 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 01538b4..a74c92a 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);
@@ -954,7 +950,7 @@ 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);
}
@@ -1029,7 +1025,6 @@ 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;
/*
@@ -1058,15 +1053,9 @@ 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));
/*
@@ -1253,14 +1242,14 @@ 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())));
}
/*
@@ -1323,7 +1312,7 @@ 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);
}
@@ -1413,7 +1402,7 @@ 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();
}
--
2.0.0
--
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