From 534d2eaf1970274150596fdd2bf552721e65d6b2 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 16 Jun 2022 02:03:12 +0200 Subject: [PATCH 1/3] random: schedule mix_interrupt_randomness() less often It used to be that mix_interrupt_randomness() would credit 1 bit each time it ran, and so add_interrupt_randomness() would schedule mix() to run every 64 interrupts, a fairly arbitrary number, but nonetheless considered to be a decent enough conservative estimate. Since e3e33fc2ea7f ("random: do not use input pool from hard IRQs"), mix() is now able to credit multiple bits, depending on the number of calls to add(). This was done for reasons separate from this commit, but it has the nice side effect of enabling this patch to schedule mix() less often. Currently the rules are: a) Credit 1 bit for every 64 calls to add(). b) Schedule mix() once a second that add() is called. c) Schedule mix() once every 64 calls to add(). Rules (a) and (c) no longer need to be coupled. It's still important to have _some_ value in (c), so that we don't "over-saturate" the fast pool, but the once per second we get from rule (b) is a plenty enough baseline. So, by increasing the 64 in rule (c) to something larger, we avoid calling queue_work_on() as frequently during irq storms. This commit changes that 64 in rule (c) to be 1024, which means we schedule mix() 16 times less often. And it does *not* need to change the 64 in rule (a). Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Cc: stable@vger.kernel.org Cc: Dominik Brodowski Acked-by: Sebastian Andrzej Siewior Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 655e327d425e..d0e4c89c4fcb 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1009,7 +1009,7 @@ void add_interrupt_randomness(int irq) if (new_count & MIX_INFLIGHT) return; - if (new_count < 64 && !time_is_before_jiffies(fast_pool->last + HZ)) + if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ)) return; if (unlikely(!fast_pool->mix.func)) From c01d4d0a82b71857be7449380338bc53dde2da92 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 16 Jun 2022 15:00:51 +0200 Subject: [PATCH 2/3] random: quiet urandom warning ratelimit suppression message random.c ratelimits how much it warns about uninitialized urandom reads using __ratelimit(). When the RNG is finally initialized, it prints the number of missed messages due to ratelimiting. It has been this way since that functionality was introduced back in 2018. Recently, cc1e127bfa95 ("random: remove ratelimiting for in-kernel unseeded randomness") put a bit more stress on the urandom ratelimiting, which teased out a bug in the implementation. Specifically, when under pressure, __ratelimit() will print its own message and reset the count back to 0, making the final message at the end less useful. Secondly, it does so as a pr_warn(), which apparently is undesirable for people's CI. Fortunately, __ratelimit() has the RATELIMIT_MSG_ON_RELEASE flag exactly for this purpose, so we set the flag. Fixes: 4e00b339e264 ("random: rate limit unseeded randomness warnings") Cc: stable@vger.kernel.org Reported-by: Jon Hunter Reported-by: Ron Economos Tested-by: Ron Economos Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 2 +- include/linux/ratelimit_types.h | 12 ++++++++---- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index d0e4c89c4fcb..07a022e24057 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -87,7 +87,7 @@ static struct fasync_struct *fasync; /* Control how we warn userspace. */ static struct ratelimit_state urandom_warning = - RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3); + RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE); static int ratelimit_disable __read_mostly = IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM); module_param_named(ratelimit_disable, ratelimit_disable, int, 0644); diff --git a/include/linux/ratelimit_types.h b/include/linux/ratelimit_types.h index c21c7f8103e2..002266693e50 100644 --- a/include/linux/ratelimit_types.h +++ b/include/linux/ratelimit_types.h @@ -23,12 +23,16 @@ struct ratelimit_state { unsigned long flags; }; -#define RATELIMIT_STATE_INIT(name, interval_init, burst_init) { \ - .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \ - .interval = interval_init, \ - .burst = burst_init, \ +#define RATELIMIT_STATE_INIT_FLAGS(name, interval_init, burst_init, flags_init) { \ + .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \ + .interval = interval_init, \ + .burst = burst_init, \ + .flags = flags_init, \ } +#define RATELIMIT_STATE_INIT(name, interval_init, burst_init) \ + RATELIMIT_STATE_INIT_FLAGS(name, interval_init, burst_init, 0) + #define RATELIMIT_STATE_INIT_DISABLED \ RATELIMIT_STATE_INIT(ratelimit_state, 0, DEFAULT_RATELIMIT_BURST) From 63b8ea5e4f1a87dea4d3114293fc8e96a8f193d7 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 20 Jun 2022 11:03:48 +0200 Subject: [PATCH 3/3] random: update comment from copy_to_user() -> copy_to_iter() This comment wasn't updated when we moved from read() to read_iter(), so this patch makes the trivial fix. Fixes: 1b388e7765f2 ("random: convert to using fops->read_iter()") Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 07a022e24057..e3dd1dd3dd22 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -408,7 +408,7 @@ static ssize_t get_random_bytes_user(struct iov_iter *iter) /* * Immediately overwrite the ChaCha key at index 4 with random - * bytes, in case userspace causes copy_to_user() below to sleep + * bytes, in case userspace causes copy_to_iter() below to sleep * forever, so that we still retain forward secrecy in that case. */ crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);