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authorJason A. Donenfeld <Jason@zx2c4.com>2017-06-07 23:06:55 -0400
committerTheodore Ts'o <tytso@mit.edu>2017-06-19 22:06:28 -0400
commitd06bfd1989fe97623b32d6df4ffa6e4338c99dc8 (patch)
tree26155c03fdfc23828c93712813a55f75b1b39e29 /lib
parent7aed9f72c3c70bdc18e72ec086c1a0eafdcd273f (diff)
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random: warn when kernel uses unseeded randomness
This enables an important dmesg notification about when drivers have used the crng without it being seeded first. Prior, these errors would occur silently, and so there hasn't been a great way of diagnosing these types of bugs for obscure setups. By adding this as a config option, we can leave it on by default, so that we learn where these issues happen, in the field, will still allowing some people to turn it off, if they really know what they're doing and do not want the log entries. However, we don't leave it _completely_ by default. An earlier version of this patch simply had `default y`. I'd really love that, but it turns out, this problem with unseeded randomness being used is really quite present and is going to take a long time to fix. Thus, as a compromise between log-messages-for-all and nobody-knows, this is `default y`, except it is also `depends on DEBUG_KERNEL`. This will ensure that the curious see the messages while others don't have to. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug16
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e4587ebe52c7..c4159605bfbf 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1209,6 +1209,22 @@ config STACKTRACE
It is also used by various kernel debugging features that require
stack trace generation.
+config WARN_UNSEEDED_RANDOM
+ bool "Warn when kernel uses unseeded randomness"
+ default y
+ depends on DEBUG_KERNEL
+ help
+ Some parts of the kernel contain bugs relating to their use of
+ cryptographically secure random numbers before it's actually possible
+ to generate those numbers securely. This setting ensures that these
+ flaws don't go unnoticed, by enabling a message, should this ever
+ occur. This will allow people with obscure setups to know when things
+ are going wrong, so that they might contact developers about fixing
+ it.
+
+ Say Y here, unless you simply do not care about using unseeded
+ randomness and do not want a potential warning message in your logs.
+
config DEBUG_KOBJECT
bool "kobject debugging"
depends on DEBUG_KERNEL