6.18-stable review patch. If anyone has any objections, please let me know.
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From: Arnd Bergmann arnd@arndb.de
[ Upstream commit 5d49f1a5bd358d24e5f88b23b46da833de1dbec8 ]
The entropy generation function keeps a local cpu mask on the stack, which can trigger warnings in configurations with a large number of CPUs:
drivers/char/random.c:1292:20: error: stack frame size (1288) exceeds limit (1280) in 'try_to_generate_entropy' [-Werror,-Wframe-larger-than]
Use the cpumask interface to dynamically allocate it in those configurations.
Fixes: 1c21fe00eda7 ("random: spread out jitter callback to different CPUs") Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/random.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c index b8b24b6ed3fe4..4ba5f0c4c8b24 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1296,6 +1296,7 @@ static void __cold try_to_generate_entropy(void) struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES); unsigned int i, num_different = 0; unsigned long last = random_get_entropy(); + cpumask_var_t timer_cpus; int cpu = -1;
for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) { @@ -1310,13 +1311,15 @@ static void __cold try_to_generate_entropy(void)
atomic_set(&stack->samples, 0); timer_setup_on_stack(&stack->timer, entropy_timer, 0); + if (!alloc_cpumask_var(&timer_cpus, GFP_KERNEL)) + goto out; + while (!crng_ready() && !signal_pending(current)) { /* * Check !timer_pending() and then ensure that any previous callback has finished * executing by checking timer_delete_sync_try(), before queueing the next one. */ if (!timer_pending(&stack->timer) && timer_delete_sync_try(&stack->timer) >= 0) { - struct cpumask timer_cpus; unsigned int num_cpus;
/* @@ -1326,19 +1329,19 @@ static void __cold try_to_generate_entropy(void) preempt_disable();
/* Only schedule callbacks on timer CPUs that are online. */ - cpumask_and(&timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); - num_cpus = cpumask_weight(&timer_cpus); + cpumask_and(timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); + num_cpus = cpumask_weight(timer_cpus); /* In very bizarre case of misconfiguration, fallback to all online. */ if (unlikely(num_cpus == 0)) { - timer_cpus = *cpu_online_mask; - num_cpus = cpumask_weight(&timer_cpus); + *timer_cpus = *cpu_online_mask; + num_cpus = cpumask_weight(timer_cpus); }
/* Basic CPU round-robin, which avoids the current CPU. */ do { - cpu = cpumask_next(cpu, &timer_cpus); + cpu = cpumask_next(cpu, timer_cpus); if (cpu >= nr_cpu_ids) - cpu = cpumask_first(&timer_cpus); + cpu = cpumask_first(timer_cpus); } while (cpu == smp_processor_id() && num_cpus > 1);
/* Expiring the timer at `jiffies` means it's the next tick. */ @@ -1354,6 +1357,8 @@ static void __cold try_to_generate_entropy(void) } mix_pool_bytes(&stack->entropy, sizeof(stack->entropy));
+ free_cpumask_var(timer_cpus); +out: timer_delete_sync(&stack->timer); timer_destroy_on_stack(&stack->timer); }