This is a note to let you know that I've just added the patch titled
random: do crng pre-init loading in worker rather than irq
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-do-crng-pre-init-loading-in-worker-rather-than-irq.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Jun 17 08:58:56 AM CEST 2022
From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
Date: Sun, 13 Feb 2022 18:25:07 +0100
Subject: random: do crng pre-init loading in worker rather than irq
From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
commit c2a7de4feb6e09f23af7accc0f882a8fa92e7ae5 upstream.
Taking spinlocks from IRQ context is generally problematic for
PREEMPT_RT. That is, in part, why we take trylocks instead. However, a
spin_try_lock() is also problematic since another spin_lock() invocation
can potentially PI-boost the wrong task, as the spin_try_lock() is
invoked from an IRQ-context, so the task on CPU (random task or idle) is
not the actual owner.
Additionally, by deferring the crng pre-init loading to the worker, we
can use the cryptographic hash function rather than xor, which is
perhaps a meaningful difference when considering this data has only been
through the relatively weak fast_mix() function.
The biggest downside of this approach is that the pre-init loading is
now deferred until later, which means things that need random numbers
after interrupts are enabled, but before workqueues are running -- or
before this particular worker manages to run -- are going to get into
trouble. Hopefully in the real world, this window is rather small,
especially since this code won't run until 64 interrupts had occurred.
Cc: Sultan Alsawaf <sultan@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Reviewed-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 65 ++++++++++++++------------------------------------
1 file changed, 19 insertions(+), 46 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -441,10 +441,6 @@ static void crng_make_state(u32 chacha_s
* boot time when it's better to have something there rather than
* nothing.
*
- * There are two paths, a slow one and a fast one. The slow one
- * hashes the input along with the current key. The fast one simply
- * xors it in, and should only be used from interrupt context.
- *
* If account is set, then the crng_init_cnt counter is incremented.
* This shouldn't be set by functions like add_device_randomness(),
* where we can't trust the buffer passed to it is guaranteed to be
@@ -453,19 +449,15 @@ static void crng_make_state(u32 chacha_s
* Returns the number of bytes processed from input, which is bounded
* by CRNG_INIT_CNT_THRESH if account is true.
*/
-static size_t crng_pre_init_inject(const void *input, size_t len,
- bool fast, bool account)
+static size_t crng_pre_init_inject(const void *input, size_t len, bool account)
{
static int crng_init_cnt = 0;
+ struct blake2s_state hash;
unsigned long flags;
- if (fast) {
- if (!spin_trylock_irqsave(&base_crng.lock, flags))
- return 0;
- } else {
- spin_lock_irqsave(&base_crng.lock, flags);
- }
+ blake2s_init(&hash, sizeof(base_crng.key));
+ spin_lock_irqsave(&base_crng.lock, flags);
if (crng_init != 0) {
spin_unlock_irqrestore(&base_crng.lock, flags);
return 0;
@@ -474,21 +466,9 @@ static size_t crng_pre_init_inject(const
if (account)
len = min_t(size_t, len, CRNG_INIT_CNT_THRESH - crng_init_cnt);
- if (fast) {
- const u8 *src = input;
- size_t i;
-
- for (i = 0; i < len; ++i)
- base_crng.key[(crng_init_cnt + i) %
- sizeof(base_crng.key)] ^= src[i];
- } else {
- struct blake2s_state hash;
-
- blake2s_init(&hash, sizeof(base_crng.key));
- blake2s_update(&hash, base_crng.key, sizeof(base_crng.key));
- blake2s_update(&hash, input, len);
- blake2s_final(&hash, base_crng.key);
- }
+ blake2s_update(&hash, base_crng.key, sizeof(base_crng.key));
+ blake2s_update(&hash, input, len);
+ blake2s_final(&hash, base_crng.key);
if (account) {
crng_init_cnt += len;
@@ -1029,7 +1009,7 @@ void add_device_randomness(const void *b
unsigned long flags, now = jiffies;
if (crng_init == 0 && size)
- crng_pre_init_inject(buf, size, false, false);
+ crng_pre_init_inject(buf, size, false);
spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(&cycles, sizeof(cycles));
@@ -1150,7 +1130,7 @@ void add_hwgenerator_randomness(const vo
size_t entropy)
{
if (unlikely(crng_init == 0)) {
- size_t ret = crng_pre_init_inject(buffer, count, false, true);
+ size_t ret = crng_pre_init_inject(buffer, count, true);
mix_pool_bytes(buffer, ret);
count -= ret;
buffer += ret;
@@ -1290,8 +1270,14 @@ static void mix_interrupt_randomness(str
fast_pool->last = jiffies;
local_irq_enable();
- mix_pool_bytes(pool, sizeof(pool));
- credit_entropy_bits(1);
+ if (unlikely(crng_init == 0)) {
+ crng_pre_init_inject(pool, sizeof(pool), true);
+ mix_pool_bytes(pool, sizeof(pool));
+ } else {
+ mix_pool_bytes(pool, sizeof(pool));
+ credit_entropy_bits(1);
+ }
+
memzero_explicit(pool, sizeof(pool));
}
@@ -1324,24 +1310,11 @@ void add_interrupt_randomness(int irq)
fast_mix(fast_pool->pool32);
new_count = ++fast_pool->count;
- if (unlikely(crng_init == 0)) {
- if (new_count >= 64 &&
- crng_pre_init_inject(fast_pool->pool32, sizeof(fast_pool->pool32),
- true, true) > 0) {
- fast_pool->count = 0;
- fast_pool->last = now;
- if (spin_trylock(&input_pool.lock)) {
- _mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32));
- spin_unlock(&input_pool.lock);
- }
- }
- return;
- }
-
if (new_count & MIX_INFLIGHT)
return;
- if (new_count < 64 && !time_after(now, fast_pool->last + HZ))
+ if (new_count < 64 && (!time_after(now, fast_pool->last + HZ) ||
+ unlikely(crng_init == 0)))
return;
if (unlikely(!fast_pool->mix.func))
Patches currently in stable-queue which might be from Jason@xxxxxxxxx are
queue-4.19/random-do-not-take-pool-spinlock-at-boot.patch
queue-4.19/random-remove-kernel.random.read_wakeup_threshold.patch
queue-4.19/random-simplify-arithmetic-function-flow-in-account.patch
queue-4.19/random-order-timer-entropy-functions-below-interrupt-functions.patch
queue-4.19/random-introduce-drain_entropy-helper-to-declutter-crng_reseed.patch
queue-4.19/random-fix-locking-in-crng_fast_load.patch
queue-4.19/random-cleanup-uuid-handling.patch
queue-4.19/random-group-userspace-read-write-functions.patch
queue-4.19/random-make-credit_entropy_bits-always-safe.patch
queue-4.19/latent_entropy-avoid-build-error-when-plugin-cflags-are-not-set.patch
queue-4.19/revert-hwrng-core-freeze-khwrng-thread-during-suspend.patch
queue-4.19/drivers-char-random.c-make-primary_crng-static.patch
queue-4.19/random-do-not-re-init-if-crng_reseed-completes-before-primary-init.patch
queue-4.19/random-use-proper-jiffies-comparison-macro.patch
queue-4.19/init-call-time_init-before-rand_initialize.patch
queue-4.19/random-split-primary-secondary-crng-init-paths.patch
queue-4.19/random-pull-add_hwgenerator_randomness-declaration-into-random.h.patch
queue-4.19/random-unify-early-init-crng-load-accounting.patch
queue-4.19/drivers-char-random.c-remove-unused-stuct-poolinfo-poolbits.patch
queue-4.19/random-use-blake2s-instead-of-sha1-in-extraction.patch
queue-4.19/random-convert-to-using-fops-write_iter.patch
queue-4.19/random-initialize-chacha20-constants-with-correct-endianness.patch
queue-4.19/random-remove-incomplete-last_data-logic.patch
queue-4.19/random-group-entropy-extraction-functions.patch
queue-4.19/random-add-proper-spdx-header.patch
queue-4.19/linux-random.h-remove-arch_has_random-arch_has_random_seed.patch
queue-4.19/random-rewrite-header-introductory-comment.patch
queue-4.19/random-make-dev-random-be-almost-like-dev-urandom.patch
queue-4.19/random-remove-ifdef-d-out-interrupt-bench.patch
queue-4.19/um-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/lib-crypto-sha1-re-roll-loops-to-reduce-code-size.patch
queue-4.19/random-tie-batched-entropy-generation-to-base_crng-generation.patch
queue-4.19/sparc-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/random-use-linear-min-entropy-accumulation-crediting.patch
queue-4.19/random-remove-batched-entropy-locking.patch
queue-4.19/xtensa-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/powerpc-remove-arch_has_random-arch_has_random_seed.patch
queue-4.19/fdt-add-support-for-rng-seed.patch
queue-4.19/random-continually-use-hwgenerator-randomness.patch
queue-4.19/random-access-input_pool_data-directly-rather-than-through-pointer.patch
queue-4.19/random-add-arch_get_random_-long_early.patch
queue-4.19/random-inline-leaves-of-rand_initialize.patch
queue-4.19/random-cleanup-poolinfo-abstraction.patch
queue-4.19/random-wire-up-fops-splice_-read-write-_iter.patch
queue-4.19/random-handle-latent-entropy-and-command-line-from-random_init.patch
queue-4.19/random-remove-use_input_pool-parameter-from-crng_reseed.patch
queue-4.19/random-credit-architectural-init-the-exact-amount.patch
queue-4.19/ia64-define-get_cycles-macro-for-arch-override.patch
queue-4.19/random-replace-custom-notifier-chain-with-standard-one.patch
queue-4.19/random-support-freezable-kthreads-in-add_hwgenerator_randomness.patch
queue-4.19/random-document-get_random_int-family.patch
queue-4.19/random-remove-the-blocking-pool.patch
queue-4.19/random-avoid-initializing-twice-in-credit-race.patch
queue-4.19/random-avoid-warnings-for-config_numa-builds.patch
queue-4.19/crypto-drbg-add-fips-140-2-ctrng-for-noise-source.patch
queue-4.19/random-mark-bootloader-randomness-code-as-__init.patch
queue-4.19/random-zero-buffer-after-reading-entropy-from-userspace.patch
queue-4.19/random-remove-whitespace-and-reorder-includes.patch
queue-4.19/random-ignore-grnd_random-in-getentropy-2.patch
queue-4.19/random-clear-fast-pool-crng-and-batches-in-cpuhp-bring-up.patch
queue-4.19/random-document-add_hwgenerator_randomness-with-other-input-functions.patch
queue-4.19/random-fix-typo-in-add_timer_randomness.patch
queue-4.19/random-do-crng-pre-init-loading-in-worker-rather-than-irq.patch
queue-4.19/powerpc-use-bool-in-archrandom.h.patch
queue-4.19/random-do-not-split-fast-init-input-in-add_hwgenerator_randomness.patch
queue-4.19/timekeeping-add-raw-clock-fallback-for-random_get_entropy.patch
queue-4.19/random-early-initialization-of-chacha-constants.patch
queue-4.19/crypto-drbg-prepare-for-more-fine-grained-tracking-of-seeding-state.patch
queue-4.19/random-delete-code-to-pull-data-into-pools.patch
queue-4.19/crypto-drbg-always-try-to-free-jitter-rng-instance.patch
queue-4.19/random-simplify-entropy-debiting.patch
queue-4.19/random-don-t-reset-crng_init_cnt-on-urandom_read.patch
queue-4.19/random-skip-fast_init-if-hwrng-provides-large-chunk-of-entropy.patch
queue-4.19/random-use-siphash-as-interrupt-entropy-accumulator.patch
queue-4.19/random-avoid-checking-crng_ready-twice-in-random_init.patch
queue-4.19/random-fix-soft-lockup-when-trying-to-read-from-an-uninitialized-blocking-pool.patch
queue-4.19/random-group-sysctl-functions.patch
queue-4.19/random-don-t-let-644-read-only-sysctls-be-written-to.patch
queue-4.19/random-document-crng_fast_key_erasure-destination-possibility.patch
queue-4.19/random-only-wake-up-writers-after-zap-if-threshold-was-passed.patch
queue-4.19/random-use-wait_event_freezable-in-add_hwgenerator_randomness.patch
queue-4.19/random-check-for-signal-and-try-earlier-when-generating-entropy.patch
queue-4.19/random-check-for-signals-every-page_size-chunk-of-dev-random.patch
queue-4.19/arm-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/random-absorb-fast-pool-into-input-pool-after-fast-load.patch
queue-4.19/random-give-sysctl_random_min_urandom_seed-a-more-sensible-value.patch
queue-4.19/crypto-blake2s-generic-c-library-implementation-and-selftest.patch
queue-4.19/random-cleanup-fractional-entropy-shift-constants.patch
queue-4.19/random-use-rdseed-instead-of-rdrand-in-entropy-extraction.patch
queue-4.19/random-move-rand_initialize-earlier.patch
queue-4.19/random-don-t-wake-crng_init_wait-when-crng_init-1.patch
queue-4.19/random-add-a-urandom_read_nowait-for-random-apis-that-don-t-warn.patch
queue-4.19/random-do-not-sign-extend-bytes-for-rotation-when-mixing.patch
queue-4.19/random-move-initialization-functions-out-of-hot-pages.patch
queue-4.19/random-remove-dead-code-left-over-from-blocking-pool.patch
queue-4.19/drivers-char-random.c-constify-poolinfo_table.patch
queue-4.19/crypto-drbg-track-whether-drbg-was-seeded-with-rng_is_initialized.patch
queue-4.19/random-use-computational-hash-for-entropy-extraction.patch
queue-4.19/random-add-and-use-pr_fmt.patch
queue-4.19/random-round-robin-registers-as-ulong-not-u32.patch
queue-4.19/random-always-wake-up-entropy-writers-after-extraction.patch
queue-4.19/s390-remove-arch_has_random-arch_has_random_seed.patch
queue-4.19/random-do-not-xor-rdrand-when-writing-into-dev-random.patch
queue-4.19/crypto-drbg-make-reseeding-from-get_random_bytes-synchronous.patch
queue-4.19/random-convert-to-entropy_bits-for-better-code-readability.patch
queue-4.19/char-random-add-a-newline-at-the-end-of-the-file.patch
queue-4.19/random-move-randomize_page-into-mm-where-it-belongs.patch
queue-4.19/random-only-call-crng_finalize_init-for-primary_crng.patch
queue-4.19/random-cleanup-integer-types.patch
queue-4.19/random-re-add-removed-comment-about-get_random_-u32-u64-reseeding.patch
queue-4.19/random-unify-cycles_t-and-jiffies-usage-and-types.patch
queue-4.19/random-insist-on-random_get_entropy-existing-in-order-to-simplify.patch
queue-4.19/random-group-initialization-wait-functions.patch
queue-4.19/linux-random.h-mark-config_arch_random-functions-__must_check.patch
queue-4.19/random-remove-unused-extract_entropy-reserved-argument.patch
queue-4.19/random-check-for-signal_pending-outside-of-need_resched-check.patch
queue-4.19/random-access-primary_pool-directly-rather-than-through-pointer.patch
queue-4.19/random-fix-sysctl-documentation-nits.patch
queue-4.19/random-remove-unused-tracepoints.patch
queue-4.19/random-only-read-from-dev-random-after-its-pool-has-received-128-bits.patch
queue-4.19/nios2-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/random-treat-bootloader-trust-toggle-the-same-way-as-cpu-trust-toggle.patch
queue-4.19/random-make-consistent-usage-of-crng_ready.patch
queue-4.19/lib-crypto-blake2s-move-hmac-construction-into-wireguard.patch
queue-4.19/parisc-define-get_cycles-macro-for-arch-override.patch
queue-4.19/x86-tsc-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/random-add-grnd_insecure-to-return-best-effort-non-cryptographic-bytes.patch
queue-4.19/crypto-drbg-move-dynamic-reseed_threshold-adjustments-to-__drbg_seed.patch
queue-4.19/random-check-for-signals-after-page-of-pool-writes.patch
queue-4.19/random-make-random_get_entropy-return-an-unsigned-long.patch
queue-4.19/random-check-for-crng_init-0-in-add_device_randomness.patch
queue-4.19/random-remove-unnecessary-unlikely.patch
queue-4.19/random-defer-fast-pool-mixing-to-worker.patch
queue-4.19/random-harmonize-crng-init-done-messages.patch
queue-4.19/crypto-blake2s-include-linux-bug.h-instead-of-asm-bug.h.patch
queue-4.19/random-use-static-branch-for-crng_ready.patch
queue-4.19/random-rather-than-entropy_store-abstraction-use-global.patch
queue-4.19/random-remove-extern-from-functions-in-header.patch
queue-4.19/siphash-use-one-source-of-truth-for-siphash-permutations.patch
queue-4.19/random-group-entropy-collection-functions.patch
queue-4.19/random-de-duplicate-input_pool-constants.patch
queue-4.19/random-mix-build-time-latent-entropy-into-pool-at-init.patch
queue-4.19/random-remove-useless-header-comment.patch
queue-4.19/linux-random.h-use-false-with-bool.patch
queue-4.19/maintainers-co-maintain-random.c.patch
queue-4.19/random-remove-outdated-int_max-6-check-in-urandom_read.patch
queue-4.19/m68k-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-4.19/alpha-define-get_cycles-macro-for-arch-override.patch
queue-4.19/random-mix-bootloader-randomness-into-pool.patch
queue-4.19/random-remove-some-dead-code-of-poolinfo.patch
queue-4.19/random-do-not-use-batches-when-crng_ready.patch
queue-4.19/crypto-drbg-always-seeded-with-sp800-90b-compliant-noise-source.patch
queue-4.19/s390-define-get_cycles-macro-for-arch-override.patch
queue-4.19/random-do-not-pretend-to-handle-premature-next-security-model.patch
queue-4.19/random-avoid-arch_get_random_seed_long-when-collecting-irq-randomness.patch
queue-4.19/random-use-is_enabled-config_numa-instead-of-ifdefs.patch
queue-4.19/random-avoid-superfluous-call-to-rdrand-in-crng-extraction.patch
queue-4.19/random-use-symbolic-constants-for-crng_init-states.patch
queue-4.19/random-reseed-more-often-immediately-after-booting.patch
queue-4.19/random-ensure-early-rdseed-goes-through-mixer-on-init.patch
queue-4.19/random-deobfuscate-irq-u32-u64-contributions.patch
queue-4.19/random-do-not-use-input-pool-from-hard-irqs.patch
queue-4.19/random-help-compiler-out-with-fast_mix-by-using-simpler-arguments.patch
queue-4.19/revert-random-use-static-branch-for-crng_ready.patch
queue-4.19/random-fix-crash-on-multiple-early-calls-to-add_bootloader_randomness.patch
queue-4.19/random-account-for-arch-randomness-in-bits.patch
queue-4.19/crypto-blake2s-adjust-include-guard-naming.patch
queue-4.19/random-do-not-allow-user-to-keep-crng-key-around-on-stack.patch
queue-4.19/x86-remove-arch_has_random-arch_has_random_seed.patch
queue-4.19/random-remove-ratelimiting-for-in-kernel-unseeded-randomness.patch
queue-4.19/random-remove-unused-irq_flags-argument-from-add_interrupt_randomness.patch
queue-4.19/random-prepend-remaining-pool-constants-with-pool_.patch
queue-4.19/powerpc-define-get_cycles-macro-for-arch-override.patch
queue-4.19/random-remove-unused-output_pool-constants.patch
queue-4.19/mips-use-fallback-for-random_get_entropy-instead-of-just-c0-random.patch
queue-4.19/random-use-hash-function-for-crng_slow_load.patch
queue-4.19/random-fix-typo-in-comments.patch
queue-4.19/random-use-proper-return-types-on-get_random_-int-long-_wait.patch
