HCoop / jackhill / guix / guix.git / blame
| Commit | Line | Data |
|---|---|---|
| dd698971 MB |
1 | Try to actively add entropy instead of waiting forever. |
| 2 | Fixes <https://bugs.gnu.org/37501>. | |
| 3 | ||
| 4 | Taken from upstream: | |
| 5 | https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=50ee7529ec4500c88f8664560770a7a1b65db72b | |
| 6 | ||
| 7 | diff --git a/drivers/char/random.c b/drivers/char/random.c | |
| 8 | index 5d5ea4ce1442..2fda6166c1dd 100644 | |
| 9 | --- a/drivers/char/random.c | |
| 10 | +++ b/drivers/char/random.c | |
| 11 | @@ -1731,6 +1731,56 @@ void get_random_bytes(void *buf, int nbytes) | |
| 12 | } | |
| 13 | EXPORT_SYMBOL(get_random_bytes); | |
| 14 | ||
| 15 | + | |
| 16 | +/* | |
| 17 | + * Each time the timer fires, we expect that we got an unpredictable | |
| 18 | + * jump in the cycle counter. Even if the timer is running on another | |
| 19 | + * CPU, the timer activity will be touching the stack of the CPU that is | |
| 20 | + * generating entropy.. | |
| 21 | + * | |
| 22 | + * Note that we don't re-arm the timer in the timer itself - we are | |
| 23 | + * happy to be scheduled away, since that just makes the load more | |
| 24 | + * complex, but we do not want the timer to keep ticking unless the | |
| 25 | + * entropy loop is running. | |
| 26 | + * | |
| 27 | + * So the re-arming always happens in the entropy loop itself. | |
| 28 | + */ | |
| 29 | +static void entropy_timer(struct timer_list *t) | |
| 30 | +{ | |
| 31 | + credit_entropy_bits(&input_pool, 1); | |
| 32 | +} | |
| 33 | + | |
| 34 | +/* | |
| 35 | + * If we have an actual cycle counter, see if we can | |
| 36 | + * generate enough entropy with timing noise | |
| 37 | + */ | |
| 38 | +static void try_to_generate_entropy(void) | |
| 39 | +{ | |
| 40 | + struct { | |
| 41 | + unsigned long now; | |
| 42 | + struct timer_list timer; | |
| 43 | + } stack; | |
| 44 | + | |
| 45 | + stack.now = random_get_entropy(); | |
| 46 | + | |
| 47 | + /* Slow counter - or none. Don't even bother */ | |
| 48 | + if (stack.now == random_get_entropy()) | |
| 49 | + return; | |
| 50 | + | |
| 51 | + timer_setup_on_stack(&stack.timer, entropy_timer, 0); | |
| 52 | + while (!crng_ready()) { | |
| 53 | + if (!timer_pending(&stack.timer)) | |
| 54 | + mod_timer(&stack.timer, jiffies+1); | |
| 55 | + mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now)); | |
| 56 | + schedule(); | |
| 57 | + stack.now = random_get_entropy(); | |
| 58 | + } | |
| 59 | + | |
| 60 | + del_timer_sync(&stack.timer); | |
| 61 | + destroy_timer_on_stack(&stack.timer); | |
| 62 | + mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now)); | |
| 63 | +} | |
| 64 | + | |
| 65 | /* | |
| 66 | * Wait for the urandom pool to be seeded and thus guaranteed to supply | |
| 67 | * cryptographically secure random numbers. This applies to: the /dev/urandom | |
| 68 | @@ -1745,7 +1795,17 @@ int wait_for_random_bytes(void) | |
| 69 | { | |
| 70 | if (likely(crng_ready())) | |
| 71 | return 0; | |
| 72 | - return wait_event_interruptible(crng_init_wait, crng_ready()); | |
| 73 | + | |
| 74 | + do { | |
| 75 | + int ret; | |
| 76 | + ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); | |
| 77 | + if (ret) | |
| 78 | + return ret > 0 ? 0 : ret; | |
| 79 | + | |
| 80 | + try_to_generate_entropy(); | |
| 81 | + } while (!crng_ready()); | |
| 82 | + | |
| 83 | + return 0; | |
| 84 | } | |
| 85 | EXPORT_SYMBOL(wait_for_random_bytes); | |
| 86 |