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author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-02-05 16:00:58 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-05-30 10:33:31 +0300 |
commit | 32d1d7ce3aada23f944e74c519687c45aa3d05b0 (patch) | |
tree | 787ba8582d1ca48fc0c957a99de0f0e8d777b10a | |
parent | 985292206167ddd2d6db65c8911417c6e8e3688d (diff) | |
download | linux-32d1d7ce3aada23f944e74c519687c45aa3d05b0.tar.xz |
random: always wake up entropy writers after extraction
commit 489c7fc44b5740d377e8cfdbf0851036e493af00 upstream.
Now that POOL_BITS == POOL_MIN_BITS, we must unconditionally wake up
entropy writers after every extraction. Therefore there's no point of
write_wakeup_threshold, so we can move it to the dustbin of unused
compatibility sysctls. While we're at it, we can fix a small comparison
where we were waking up after <= min rather than < min.
Cc: Theodore Ts'o <tytso@mit.edu>
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 7 | ||||
-rw-r--r-- | drivers/char/random.c | 33 |
2 files changed, 16 insertions, 24 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index e338306f4587..ffc392289c68 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1011,14 +1011,17 @@ This is a directory, with the following entries: * ``poolsize``: the entropy pool size, in bits; * ``urandom_min_reseed_secs``: obsolete (used to determine the minimum - number of seconds between urandom pool reseeding). + number of seconds between urandom pool reseeding). This file is + writable for compatibility purposes, but writing to it has no effect + on any RNG behavior. * ``uuid``: a UUID generated every time this is retrieved (this can thus be used to generate UUIDs at will); * ``write_wakeup_threshold``: when the entropy count drops below this (as a number of bits), processes waiting to write to ``/dev/random`` - are woken up. + are woken up. This file is writable for compatibility purposes, but + writing to it has no effect on any RNG behavior. If ``drivers/char/random.c`` is built with ``ADD_INTERRUPT_BENCH`` defined, these additional entries are present: diff --git a/drivers/char/random.c b/drivers/char/random.c index f678620a25f8..6e8176f4a448 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -296,12 +296,6 @@ enum { */ static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); static struct fasync_struct *fasync; -/* - * If the entropy count falls under this number of bits, then we - * should wake up processes which are selecting or polling on write - * access to /dev/random. - */ -static int random_write_wakeup_bits = POOL_MIN_BITS; static DEFINE_SPINLOCK(random_ready_list_lock); static LIST_HEAD(random_ready_list); @@ -739,10 +733,8 @@ static void crng_reseed(struct crng_state *crng, bool use_input_pool) return; } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); extract_entropy(buf.key, sizeof(buf.key)); - if (random_write_wakeup_bits) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); } else { _extract_crng(&primary_crng, buf.block); _crng_backtrack_protect(&primary_crng, buf.block, @@ -1471,7 +1463,7 @@ static __poll_t random_poll(struct file *file, poll_table *wait) mask = 0; if (crng_ready()) mask |= EPOLLIN | EPOLLRDNORM; - if (input_pool.entropy_count < random_write_wakeup_bits) + if (input_pool.entropy_count < POOL_MIN_BITS) mask |= EPOLLOUT | EPOLLWRNORM; return mask; } @@ -1556,7 +1548,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; - if (xchg(&input_pool.entropy_count, 0) && random_write_wakeup_bits) { + if (xchg(&input_pool.entropy_count, 0)) { wake_up_interruptible(&random_write_wait); kill_fasync(&fasync, SIGIO, POLL_OUT); } @@ -1636,9 +1628,9 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, #include <linux/sysctl.h> -static int min_write_thresh; -static int max_write_thresh = POOL_BITS; static int random_min_urandom_seed = 60; +static int random_write_wakeup_bits = POOL_MIN_BITS; +static int sysctl_poolsize = POOL_BITS; static char sysctl_bootid[16]; /* @@ -1677,7 +1669,6 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, return proc_dostring(&fake_table, write, buffer, lenp, ppos); } -static int sysctl_poolsize = POOL_BITS; extern struct ctl_table random_table[]; struct ctl_table random_table[] = { { @@ -1699,9 +1690,7 @@ struct ctl_table random_table[] = { .data = &random_write_wakeup_bits, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = &min_write_thresh, - .extra2 = &max_write_thresh, + .proc_handler = proc_dointvec, }, { .procname = "urandom_min_reseed_secs", @@ -1882,13 +1871,13 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, } /* Throttle writing if we're above the trickle threshold. - * We'll be woken up again once below random_write_wakeup_thresh, - * when the calling thread is about to terminate, or once - * CRNG_RESEED_INTERVAL has lapsed. + * We'll be woken up again once below POOL_MIN_BITS, when + * the calling thread is about to terminate, or once + * CRNG_RESEED_INTERVAL has elapsed. */ wait_event_interruptible_timeout(random_write_wait, !system_wq || kthread_should_stop() || - input_pool.entropy_count <= random_write_wakeup_bits, + input_pool.entropy_count < POOL_MIN_BITS, CRNG_RESEED_INTERVAL); mix_pool_bytes(buffer, count); credit_entropy_bits(entropy); |