summaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
authorJason A. Donenfeld <Jason@zx2c4.com>2022-05-09 16:13:18 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-05-18 15:53:53 +0200
commitcc1e127bfa95b5fb2f9307e7168bf8b2b45b4c5e (patch)
tree9543ce658d5e3986da5fd945b8091cfdb0396a30 /lib
parent68c9c8b192c6dae9be6278e98ee44029d5da2d31 (diff)
random: remove ratelimiting for in-kernel unseeded randomness
The CONFIG_WARN_ALL_UNSEEDED_RANDOM debug option controls whether the kernel warns about all unseeded randomness or just the first instance. There's some complicated rate limiting and comparison to the previous caller, such that even with CONFIG_WARN_ALL_UNSEEDED_RANDOM enabled, developers still don't see all the messages or even an accurate count of how many were missed. This is the result of basically parallel mechanisms aimed at accomplishing more or less the same thing, added at different points in random.c history, which sort of compete with the first-instance-only limiting we have now. It turns out, however, that nobody cares about the first unseeded randomness instance of in-kernel users. The same first user has been there for ages now, and nobody is doing anything about it. It isn't even clear that anybody _can_ do anything about it. Most places that can do something about it have switched over to using get_random_bytes_wait() or wait_for_random_bytes(), which is the right thing to do, but there is still much code that needs randomness sometimes during init, and as a geeneral rule, if you're not using one of the _wait functions or the readiness notifier callback, you're bound to be doing it wrong just based on that fact alone. So warning about this same first user that can't easily change is simply not an effective mechanism for anything at all. Users can't do anything about it, as the Kconfig text points out -- the problem isn't in userspace code -- and kernel developers don't or more often can't react to it. Instead, show the warning for all instances when CONFIG_WARN_ALL_UNSEEDED_RANDOM is set, so that developers can debug things need be, or if it isn't set, don't show a warning at all. At the same time, CONFIG_WARN_ALL_UNSEEDED_RANDOM now implies setting random.ratelimit_disable=1 on by default, since if you care about one you probably care about the other too. And we can clean up usage around the related urandom_warning ratelimiter as well (whose behavior isn't changing), so that it properly counts missed messages after the 10 message threshold is reached. Cc: Theodore Ts'o <tytso@mit.edu> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug3
1 files changed, 1 insertions, 2 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 075cd25363ac..7e282970177a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1616,8 +1616,7 @@ config WARN_ALL_UNSEEDED_RANDOM
so architecture maintainers really need to do what they can
to get the CRNG seeded sooner after the system is booted.
However, since users cannot do anything actionable to
- address this, by default the kernel will issue only a single
- warning for the first use of unseeded randomness.
+ address this, by default this option is disabled.
Say Y here if you want to receive warnings for all uses of
unseeded randomness. This will be of use primarily for