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A few random (cough, cough) cleanups for the /dev/random driver 

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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random updates from Ted Ts'o:
 "A few random (cough, cough) cleanups for the /dev/random driver"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  drivers/char/random.c: remove unused dont_count_entropy
  random: optimize add_interrupt_randomness
  random: always fill buffer in get_random_bytes_wait
  random: use a tighter cap in credit_entropy_bits_safe()
This commit is contained in:
Linus Torvalds 2018-04-04 14:31:53 -07:00
parent 3e968c9f14 5e747dd9be
commit 0c21fd6e65
2 changed files with 26 additions and 30 deletions
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52
drivers/char/random.c
View File

@ -709,7 +709,8 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
}
/* should we wake readers? */
if (entropy_bits >= random_read_wakeup_bits) {
if (entropy_bits >= random_read_wakeup_bits &&
wq_has_sleeper(&random_read_wait)) {
wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
@ -732,7 +733,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
{
const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
const int nbits_max = r->poolinfo->poolwords * 32;
if (nbits < 0)
return -EINVAL;
@ -963,7 +964,6 @@ static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
struct timer_rand_state {
cycles_t last_time;
long last_delta, last_delta2;
unsigned dont_count_entropy:1;
};
#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
@ -1029,35 +1029,33 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
* We take into account the first, second and third-order deltas
* in order to make our estimate.
*/
delta = sample.jiffies - state->last_time;
state->last_time = sample.jiffies;
if (!state->dont_count_entropy) {
delta = sample.jiffies - state->last_time;
state->last_time = sample.jiffies;
delta2 = delta - state->last_delta;
state->last_delta = delta;
delta2 = delta - state->last_delta;
state->last_delta = delta;
delta3 = delta2 - state->last_delta2;
state->last_delta2 = delta2;
delta3 = delta2 - state->last_delta2;
state->last_delta2 = delta2;
if (delta < 0)
delta = -delta;
if (delta2 < 0)
delta2 = -delta2;
if (delta3 < 0)
delta3 = -delta3;
if (delta > delta2)
delta = delta2;
if (delta > delta3)
delta = delta3;
if (delta < 0)
delta = -delta;
if (delta2 < 0)
delta2 = -delta2;
if (delta3 < 0)
delta3 = -delta3;
if (delta > delta2)
delta = delta2;
if (delta > delta3)
delta = delta3;
/*
* delta is now minimum absolute delta.
* Round down by 1 bit on general principles,
* and limit entropy entimate to 12 bits.
*/
credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
/*
* delta is now minimum absolute delta.
* Round down by 1 bit on general principles,
* and limit entropy entimate to 12 bits.
*/
credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
}
preempt_enable();
}

4
include/linux/random.h
View File

@ -85,10 +85,8 @@ static inline unsigned long get_random_canary(void)
static inline int get_random_bytes_wait(void *buf, int nbytes)
{
int ret = wait_for_random_bytes();
if (unlikely(ret))
return ret;
get_random_bytes(buf, nbytes);
return 0;
return ret;
}
#define declare_get_random_var_wait(var) \