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authorLinus Torvalds <torvalds@linux-foundation.org>2017-07-15 12:44:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-15 12:44:02 -0700
commit52f6c588c77b76d548201470c2a28263a41b462b (patch)
treecbb4207714e82f10932a546469bfb3db84051c33 /lib
parent78dcf73421a879d22319d3889119945b85954a68 (diff)
parent72e5c740f6335e27253b8ff64d23d00337091535 (diff)
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random
Pull random updates from Ted Ts'o: "Add wait_for_random_bytes() and get_random_*_wait() functions so that callers can more safely get random bytes if they can block until the CRNG is initialized. Also print a warning if get_random_*() is called before the CRNG is initialized. By default, only one single-line warning will be printed per boot. If CONFIG_WARN_ALL_UNSEEDED_RANDOM is defined, then a warning will be printed for each function which tries to get random bytes before the CRNG is initialized. This can get spammy for certain architecture types, so it is not enabled by default" * tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random: random: reorder READ_ONCE() in get_random_uXX random: suppress spammy warnings about unseeded randomness random: warn when kernel uses unseeded randomness net/route: use get_random_int for random counter net/neighbor: use get_random_u32 for 32-bit hash random rhashtable: use get_random_u32 for hash_rnd ceph: ensure RNG is seeded before using iscsi: ensure RNG is seeded before use cifs: use get_random_u32 for 32-bit lock random random: add get_random_{bytes,u32,u64,int,long,once}_wait family random: add wait_for_random_bytes() API
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug28
-rw-r--r--lib/rhashtable.c2
2 files changed, 29 insertions, 1 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 789c6e9e5e01..98fe715522e8 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1223,6 +1223,34 @@ config STACKTRACE
It is also used by various kernel debugging features that require
stack trace generation.
+config WARN_ALL_UNSEEDED_RANDOM
+ bool "Warn for all uses of unseeded randomness"
+ default n
+ 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.
+
+ Unfortunately, on some models of some architectures getting
+ a fully seeded CRNG is extremely difficult, and so this can
+ result in dmesg getting spammed for a surprisingly long
+ time. This is really bad from a security perspective, and
+ so architecture maintainers really need to do what they can
+ to get the CRNG seeded sooner after the system is booted.
+ However, since users can not do anything actionble to
+ address this, by default the kernel will issue only a single
+ warning for the first use of unseeded randomness.
+
+ Say Y here if you want to receive warnings for all uses of
+ unseeded randomness. This will be of use primarily for
+ those developers interersted in improving the security of
+ Linux kernels running on their architecture (or
+ subarchitecture).
+
config DEBUG_KOBJECT
bool "kobject debugging"
depends on DEBUG_KERNEL
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 42466c167257..707ca5d677c6 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -234,7 +234,7 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
INIT_LIST_HEAD(&tbl->walkers);
- get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
+ tbl->hash_rnd = get_random_u32();
for (i = 0; i < nbuckets; i++)
INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);