diff options
Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index a4bea7775e0f..c35cee268e13 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1294,6 +1294,34 @@ void rand_initialize_disk(struct gendisk *disk) } #endif +/* + * Attempt an emergency refill using arch_get_random_seed_long(). + * + * As with add_interrupt_randomness() be paranoid and only + * credit the output as 50% entropic. + */ +static int arch_random_refill(void) +{ + const unsigned int nlongs = 64; /* Arbitrary number */ + unsigned int n = 0; + unsigned int i; + unsigned long buf[nlongs]; + + for (i = 0; i < nlongs; i++) { + if (arch_get_random_seed_long(&buf[n])) + n++; + } + + if (n) { + unsigned int rand_bytes = n * sizeof(unsigned long); + + mix_pool_bytes(&input_pool, buf, rand_bytes, NULL); + credit_entropy_bits(&input_pool, rand_bytes*4); + } + + return n; +} + static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { @@ -1312,8 +1340,13 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) ENTROPY_BITS(&input_pool)); if (n > 0) return n; + /* Pool is (near) empty. Maybe wait and retry. */ + /* First try an emergency refill */ + if (arch_random_refill()) + continue; + if (file->f_flags & O_NONBLOCK) return -EAGAIN; |