This is a note to let you know that I've just added the patch titled random: check for signals after page of pool writes to the 4.14-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-check-for-signals-after-page-of-pool-writes.patch and it can be found in the queue-4.14 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 Thu Jun 16 07:08:33 PM CEST 2022 From: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Date: Sun, 22 May 2022 22:25:41 +0200 Subject: random: check for signals after page of pool writes From: "Jason A. Donenfeld" <Jason@xxxxxxxxx> commit 1ce6c8d68f8ac587f54d0a271ac594d3d51f3efb upstream. get_random_bytes_user() checks for signals after producing a PAGE_SIZE worth of output, just like /dev/zero does. write_pool() is doing basically the same work (actually, slightly more expensive), and so should stop to check for signals in the same way. Let's also name it write_pool_user() to match get_random_bytes_user(), so this won't be misused in the future. Before this patch, massive writes to /dev/urandom would tie up the process for an extremely long time and make it unterminatable. After, it can be successfully interrupted. The following test program can be used to see this works as intended: #include <unistd.h> #include <fcntl.h> #include <signal.h> #include <stdio.h> static unsigned char x[~0U]; static void handle(int) { } int main(int argc, char *argv[]) { pid_t pid = getpid(), child; int fd; signal(SIGUSR1, handle); if (!(child = fork())) { for (;;) kill(pid, SIGUSR1); } fd = open("/dev/urandom", O_WRONLY); pause(); printf("interrupted after writing %zd bytes\n", write(fd, x, sizeof(x))); close(fd); kill(child, SIGTERM); return 0; } Result before: "interrupted after writing 2147479552 bytes" Result after: "interrupted after writing 4096 bytes" Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/char/random.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1251,7 +1251,7 @@ static unsigned int random_poll(struct f return crng_ready() ? POLLIN | POLLRDNORM : POLLOUT | POLLWRNORM; } -static ssize_t write_pool(struct iov_iter *iter) +static ssize_t write_pool_user(struct iov_iter *iter) { u8 block[BLAKE2S_BLOCK_SIZE]; ssize_t ret = 0; @@ -1266,7 +1266,13 @@ static ssize_t write_pool(struct iov_ite mix_pool_bytes(block, copied); if (!iov_iter_count(iter) || copied != sizeof(block)) break; - cond_resched(); + + BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0); + if (ret % PAGE_SIZE == 0) { + if (signal_pending(current)) + break; + cond_resched(); + } } memzero_explicit(block, sizeof(block)); @@ -1275,7 +1281,7 @@ static ssize_t write_pool(struct iov_ite static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter) { - return write_pool(iter); + return write_pool_user(iter); } static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter) @@ -1342,7 +1348,7 @@ static long random_ioctl(struct file *f, ret = import_single_range(WRITE, p, len, &iov, &iter); if (unlikely(ret)) return ret; - ret = write_pool(&iter); + ret = write_pool_user(&iter); if (unlikely(ret < 0)) return ret; /* Since we're crediting, enforce that it was all written into the pool. */ Patches currently in stable-queue which might be from Jason@xxxxxxxxx are queue-4.14/random-do-not-take-pool-spinlock-at-boot.patch queue-4.14/random-remove-kernel.random.read_wakeup_threshold.patch queue-4.14/random-simplify-arithmetic-function-flow-in-account.patch queue-4.14/random-order-timer-entropy-functions-below-interrupt-functions.patch queue-4.14/random-introduce-drain_entropy-helper-to-declutter-crng_reseed.patch queue-4.14/random-fix-locking-in-crng_fast_load.patch queue-4.14/random-cleanup-uuid-handling.patch queue-4.14/random-group-userspace-read-write-functions.patch queue-4.14/random-make-credit_entropy_bits-always-safe.patch queue-4.14/latent_entropy-avoid-build-error-when-plugin-cflags-are-not-set.patch queue-4.14/revert-hwrng-core-freeze-khwrng-thread-during-suspend.patch queue-4.14/drivers-char-random.c-make-primary_crng-static.patch queue-4.14/random-do-not-re-init-if-crng_reseed-completes-before-primary-init.patch queue-4.14/random-always-fill-buffer-in-get_random_bytes_wait.patch queue-4.14/random-use-proper-jiffies-comparison-macro.patch queue-4.14/init-call-time_init-before-rand_initialize.patch queue-4.14/random-split-primary-secondary-crng-init-paths.patch queue-4.14/random-pull-add_hwgenerator_randomness-declaration-into-random.h.patch queue-4.14/random-unify-early-init-crng-load-accounting.patch queue-4.14/drivers-char-random.c-remove-unused-stuct-poolinfo-poolbits.patch queue-4.14/random-use-blake2s-instead-of-sha1-in-extraction.patch queue-4.14/random-make-cpu-trust-a-boot-parameter.patch queue-4.14/random-convert-to-using-fops-write_iter.patch queue-4.14/random-initialize-chacha20-constants-with-correct-endianness.patch queue-4.14/random-remove-incomplete-last_data-logic.patch queue-4.14/random-group-entropy-extraction-functions.patch queue-4.14/random-optimize-add_interrupt_randomness.patch queue-4.14/random-add-proper-spdx-header.patch queue-4.14/linux-random.h-remove-arch_has_random-arch_has_random_seed.patch queue-4.14/random-rewrite-header-introductory-comment.patch queue-4.14/random-make-dev-random-be-almost-like-dev-urandom.patch queue-4.14/random-remove-ifdef-d-out-interrupt-bench.patch queue-4.14/um-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/lib-crypto-sha1-re-roll-loops-to-reduce-code-size.patch queue-4.14/random-tie-batched-entropy-generation-to-base_crng-generation.patch queue-4.14/sparc-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/random-use-linear-min-entropy-accumulation-crediting.patch queue-4.14/random-remove-batched-entropy-locking.patch queue-4.14/xtensa-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/powerpc-remove-arch_has_random-arch_has_random_seed.patch queue-4.14/fdt-add-support-for-rng-seed.patch queue-4.14/random-continually-use-hwgenerator-randomness.patch queue-4.14/random-access-input_pool_data-directly-rather-than-through-pointer.patch queue-4.14/random-add-arch_get_random_-long_early.patch queue-4.14/random-inline-leaves-of-rand_initialize.patch queue-4.14/random-cleanup-poolinfo-abstraction.patch queue-4.14/random-wire-up-fops-splice_-read-write-_iter.patch queue-4.14/random-handle-latent-entropy-and-command-line-from-random_init.patch queue-4.14/random-remove-use_input_pool-parameter-from-crng_reseed.patch queue-4.14/random-credit-architectural-init-the-exact-amount.patch queue-4.14/ia64-define-get_cycles-macro-for-arch-override.patch queue-4.14/random-replace-custom-notifier-chain-with-standard-one.patch queue-4.14/random-support-freezable-kthreads-in-add_hwgenerator_randomness.patch queue-4.14/random-document-get_random_int-family.patch queue-4.14/random-remove-the-blocking-pool.patch queue-4.14/random-avoid-initializing-twice-in-credit-race.patch queue-4.14/random-avoid-warnings-for-config_numa-builds.patch queue-4.14/crypto-drbg-add-fips-140-2-ctrng-for-noise-source.patch queue-4.14/random-mark-bootloader-randomness-code-as-__init.patch queue-4.14/random-zero-buffer-after-reading-entropy-from-userspace.patch queue-4.14/random-remove-whitespace-and-reorder-includes.patch queue-4.14/random-ignore-grnd_random-in-getentropy-2.patch queue-4.14/random-clear-fast-pool-crng-and-batches-in-cpuhp-bring-up.patch queue-4.14/random-document-add_hwgenerator_randomness-with-other-input-functions.patch queue-4.14/random-fix-typo-in-add_timer_randomness.patch queue-4.14/random-do-crng-pre-init-loading-in-worker-rather-than-irq.patch queue-4.14/powerpc-use-bool-in-archrandom.h.patch queue-4.14/random-do-not-split-fast-init-input-in-add_hwgenerator_randomness.patch queue-4.14/timekeeping-add-raw-clock-fallback-for-random_get_entropy.patch queue-4.14/random-early-initialization-of-chacha-constants.patch queue-4.14/crypto-drbg-prepare-for-more-fine-grained-tracking-of-seeding-state.patch queue-4.14/random-delete-code-to-pull-data-into-pools.patch queue-4.14/crypto-drbg-always-try-to-free-jitter-rng-instance.patch queue-4.14/random-simplify-entropy-debiting.patch queue-4.14/random-don-t-reset-crng_init_cnt-on-urandom_read.patch queue-4.14/random-skip-fast_init-if-hwrng-provides-large-chunk-of-entropy.patch queue-4.14/random-use-siphash-as-interrupt-entropy-accumulator.patch queue-4.14/random-avoid-checking-crng_ready-twice-in-random_init.patch queue-4.14/random-fix-soft-lockup-when-trying-to-read-from-an-uninitialized-blocking-pool.patch queue-4.14/random-group-sysctl-functions.patch queue-4.14/random-don-t-let-644-read-only-sysctls-be-written-to.patch queue-4.14/random-document-crng_fast_key_erasure-destination-possibility.patch queue-4.14/random-only-wake-up-writers-after-zap-if-threshold-was-passed.patch queue-4.14/random-use-wait_event_freezable-in-add_hwgenerator_randomness.patch queue-4.14/random-check-for-signal-and-try-earlier-when-generating-entropy.patch queue-4.14/random-check-for-signals-every-page_size-chunk-of-dev-random.patch queue-4.14/arm-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/random-absorb-fast-pool-into-input-pool-after-fast-load.patch queue-4.14/random-give-sysctl_random_min_urandom_seed-a-more-sensible-value.patch queue-4.14/crypto-blake2s-generic-c-library-implementation-and-selftest.patch queue-4.14/random-cleanup-fractional-entropy-shift-constants.patch queue-4.14/random-use-rdseed-instead-of-rdrand-in-entropy-extraction.patch queue-4.14/random-move-rand_initialize-earlier.patch queue-4.14/random-don-t-wake-crng_init_wait-when-crng_init-1.patch queue-4.14/random-add-a-urandom_read_nowait-for-random-apis-that-don-t-warn.patch queue-4.14/random-do-not-sign-extend-bytes-for-rotation-when-mixing.patch queue-4.14/random-move-initialization-functions-out-of-hot-pages.patch queue-4.14/random-remove-dead-code-left-over-from-blocking-pool.patch queue-4.14/drivers-char-random.c-constify-poolinfo_table.patch queue-4.14/crypto-drbg-track-whether-drbg-was-seeded-with-rng_is_initialized.patch queue-4.14/random-use-computational-hash-for-entropy-extraction.patch queue-4.14/random-add-and-use-pr_fmt.patch queue-4.14/random-round-robin-registers-as-ulong-not-u32.patch queue-4.14/random-always-wake-up-entropy-writers-after-extraction.patch queue-4.14/s390-remove-arch_has_random-arch_has_random_seed.patch queue-4.14/random-do-not-xor-rdrand-when-writing-into-dev-random.patch queue-4.14/crypto-drbg-make-reseeding-from-get_random_bytes-synchronous.patch queue-4.14/random-convert-to-entropy_bits-for-better-code-readability.patch queue-4.14/char-random-add-a-newline-at-the-end-of-the-file.patch queue-4.14/random-move-randomize_page-into-mm-where-it-belongs.patch queue-4.14/random-only-call-crng_finalize_init-for-primary_crng.patch queue-4.14/random-cleanup-integer-types.patch queue-4.14/random-re-add-removed-comment-about-get_random_-u32-u64-reseeding.patch queue-4.14/random-unify-cycles_t-and-jiffies-usage-and-types.patch queue-4.14/random-insist-on-random_get_entropy-existing-in-order-to-simplify.patch queue-4.14/random-group-initialization-wait-functions.patch queue-4.14/linux-random.h-mark-config_arch_random-functions-__must_check.patch queue-4.14/random-remove-unused-extract_entropy-reserved-argument.patch queue-4.14/random-check-for-signal_pending-outside-of-need_resched-check.patch queue-4.14/random-access-primary_pool-directly-rather-than-through-pointer.patch queue-4.14/random-fix-sysctl-documentation-nits.patch queue-4.14/random-remove-unused-tracepoints.patch queue-4.14/random-only-read-from-dev-random-after-its-pool-has-received-128-bits.patch queue-4.14/nios2-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/random-treat-bootloader-trust-toggle-the-same-way-as-cpu-trust-toggle.patch queue-4.14/random-make-consistent-usage-of-crng_ready.patch queue-4.14/lib-crypto-blake2s-move-hmac-construction-into-wireguard.patch queue-4.14/parisc-define-get_cycles-macro-for-arch-override.patch queue-4.14/x86-tsc-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/crypto-chacha20-fix-keystream-alignment-for-chacha20_block.patch queue-4.14/random-add-grnd_insecure-to-return-best-effort-non-cryptographic-bytes.patch queue-4.14/random-fix-whitespace-pre-random-bytes-work.patch queue-4.14/crypto-drbg-move-dynamic-reseed_threshold-adjustments-to-__drbg_seed.patch queue-4.14/random-check-for-signals-after-page-of-pool-writes.patch queue-4.14/random-make-random_get_entropy-return-an-unsigned-long.patch queue-4.14/random-check-for-crng_init-0-in-add_device_randomness.patch queue-4.14/random-add-a-config-option-to-trust-the-cpu-s-hwrng.patch queue-4.14/random-remove-unnecessary-unlikely.patch queue-4.14/random-defer-fast-pool-mixing-to-worker.patch queue-4.14/random-harmonize-crng-init-done-messages.patch queue-4.14/crypto-blake2s-include-linux-bug.h-instead-of-asm-bug.h.patch queue-4.14/random-use-static-branch-for-crng_ready.patch queue-4.14/random-rather-than-entropy_store-abstraction-use-global.patch queue-4.14/drivers-char-random.c-remove-unused-dont_count_entropy.patch queue-4.14/random-remove-extern-from-functions-in-header.patch queue-4.14/siphash-use-one-source-of-truth-for-siphash-permutations.patch queue-4.14/random-group-entropy-collection-functions.patch queue-4.14/random-de-duplicate-input_pool-constants.patch queue-4.14/random-mix-build-time-latent-entropy-into-pool-at-init.patch queue-4.14/random-remove-useless-header-comment.patch queue-4.14/linux-random.h-use-false-with-bool.patch queue-4.14/maintainers-co-maintain-random.c.patch queue-4.14/random-remove-outdated-int_max-6-check-in-urandom_read.patch queue-4.14/m68k-use-fallback-for-random_get_entropy-instead-of-zero.patch queue-4.14/alpha-define-get_cycles-macro-for-arch-override.patch queue-4.14/random-mix-bootloader-randomness-into-pool.patch queue-4.14/random-remove-some-dead-code-of-poolinfo.patch queue-4.14/random-do-not-use-batches-when-crng_ready.patch queue-4.14/crypto-drbg-always-seeded-with-sp800-90b-compliant-noise-source.patch queue-4.14/s390-define-get_cycles-macro-for-arch-override.patch queue-4.14/random-do-not-pretend-to-handle-premature-next-security-model.patch queue-4.14/random-avoid-arch_get_random_seed_long-when-collecting-irq-randomness.patch queue-4.14/random-use-is_enabled-config_numa-instead-of-ifdefs.patch queue-4.14/random-make-crng-state-queryable.patch queue-4.14/random-avoid-superfluous-call-to-rdrand-in-crng-extraction.patch queue-4.14/random-use-symbolic-constants-for-crng_init-states.patch queue-4.14/random-reseed-more-often-immediately-after-booting.patch queue-4.14/random-ensure-early-rdseed-goes-through-mixer-on-init.patch queue-4.14/random-deobfuscate-irq-u32-u64-contributions.patch queue-4.14/random-do-not-use-input-pool-from-hard-irqs.patch queue-4.14/random-help-compiler-out-with-fast_mix-by-using-simpler-arguments.patch queue-4.14/revert-random-use-static-branch-for-crng_ready.patch queue-4.14/random-fix-crash-on-multiple-early-calls-to-add_bootloader_randomness.patch queue-4.14/random-return-nbytes-filled-from-hw-rng.patch queue-4.14/random-account-for-arch-randomness-in-bits.patch queue-4.14/crypto-blake2s-adjust-include-guard-naming.patch queue-4.14/random-do-not-allow-user-to-keep-crng-key-around-on-stack.patch queue-4.14/x86-remove-arch_has_random-arch_has_random_seed.patch queue-4.14/crypto-deduplicate-le32_to_cpu_array-and-cpu_to_le32_array.patch queue-4.14/random-remove-ratelimiting-for-in-kernel-unseeded-randomness.patch queue-4.14/random-remove-unused-irq_flags-argument-from-add_interrupt_randomness.patch queue-4.14/random-prepend-remaining-pool-constants-with-pool_.patch queue-4.14/powerpc-define-get_cycles-macro-for-arch-override.patch queue-4.14/random-remove-unused-output_pool-constants.patch queue-4.14/mips-use-fallback-for-random_get_entropy-instead-of-just-c0-random.patch queue-4.14/random-use-hash-function-for-crng_slow_load.patch queue-4.14/random-fix-typo-in-comments.patch queue-4.14/random-remove-preempt-disabled-region.patch queue-4.14/random-use-proper-return-types-on-get_random_-int-long-_wait.patch