diff options
| -rw-r--r-- | drivers/char/random.c | 56 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 24 |
2 files changed, 57 insertions, 23 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index fa5bbd5a7ca0..799d37981d99 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -436,6 +436,7 @@ static void _extract_crng(struct crng_state *crng, static void _crng_backtrack_protect(struct crng_state *crng, __u8 tmp[CHACHA20_BLOCK_SIZE], int used); static void process_random_ready_list(void); +static void _get_random_bytes(void *buf, int nbytes); /********************************************************************** * @@ -776,7 +777,7 @@ static void crng_initialize(struct crng_state *crng) _extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0); else - get_random_bytes(&crng->state[4], sizeof(__u32) * 12); + _get_random_bytes(&crng->state[4], sizeof(__u32) * 12); for (i = 4; i < 16; i++) { if (!arch_get_random_seed_long(&rv) && !arch_get_random_long(&rv)) @@ -1466,6 +1467,30 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, return ret; } +#define warn_unseeded_randomness(previous) \ + _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous)) + +static void _warn_unseeded_randomness(const char *func_name, void *caller, + void **previous) +{ +#ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM + const bool print_once = false; +#else + static bool print_once __read_mostly; +#endif + + if (print_once || + crng_ready() || + (previous && (caller == READ_ONCE(*previous)))) + return; + WRITE_ONCE(*previous, caller); +#ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM + print_once = true; +#endif + pr_notice("random: %s called from %pF with crng_init=%d\n", + func_name, caller, crng_init); +} + /* * This function is the exported kernel interface. It returns some * number of good random numbers, suitable for key generation, seeding @@ -1476,15 +1501,10 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, * wait_for_random_bytes() should be called and return 0 at least once * at any point prior. */ -void get_random_bytes(void *buf, int nbytes) +static void _get_random_bytes(void *buf, int nbytes) { __u8 tmp[CHACHA20_BLOCK_SIZE]; -#ifdef CONFIG_WARN_UNSEEDED_RANDOM - if (!crng_ready()) - printk(KERN_NOTICE "random: %pF get_random_bytes called " - "with crng_init = %d\n", (void *) _RET_IP_, crng_init); -#endif trace_get_random_bytes(nbytes, _RET_IP_); while (nbytes >= CHACHA20_BLOCK_SIZE) { @@ -1501,6 +1521,14 @@ void get_random_bytes(void *buf, int nbytes) crng_backtrack_protect(tmp, CHACHA20_BLOCK_SIZE); memzero_explicit(tmp, sizeof(tmp)); } + +void get_random_bytes(void *buf, int nbytes) +{ + static void *previous; + + warn_unseeded_randomness(&previous); + _get_random_bytes(buf, nbytes); +} EXPORT_SYMBOL(get_random_bytes); /* @@ -2064,6 +2092,7 @@ u64 get_random_u64(void) bool use_lock = READ_ONCE(crng_init) < 2; unsigned long flags = 0; struct batched_entropy *batch; + static void *previous; #if BITS_PER_LONG == 64 if (arch_get_random_long((unsigned long *)&ret)) @@ -2074,11 +2103,7 @@ u64 get_random_u64(void) return ret; #endif -#ifdef CONFIG_WARN_UNSEEDED_RANDOM - if (!crng_ready()) - printk(KERN_NOTICE "random: %pF get_random_u64 called " - "with crng_init = %d\n", (void *) _RET_IP_, crng_init); -#endif + warn_unseeded_randomness(&previous); batch = &get_cpu_var(batched_entropy_u64); if (use_lock) @@ -2102,15 +2127,12 @@ u32 get_random_u32(void) bool use_lock = READ_ONCE(crng_init) < 2; unsigned long flags = 0; struct batched_entropy *batch; + static void *previous; if (arch_get_random_int(&ret)) return ret; -#ifdef CONFIG_WARN_UNSEEDED_RANDOM - if (!crng_ready()) - printk(KERN_NOTICE "random: %pF get_random_u32 called " - "with crng_init = %d\n", (void *) _RET_IP_, crng_init); -#endif + warn_unseeded_randomness(&previous); batch = &get_cpu_var(batched_entropy_u32); if (use_lock) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index c4159605bfbf..9d0a244074b9 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1209,10 +1209,9 @@ 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 +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 @@ -1222,8 +1221,21 @@ config WARN_UNSEEDED_RANDOM 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. + 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" |