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random: move rand_initialize() earlier 

Right now rand_initialize() is run as an early_initcall(), but it only
depends on timekeeping_init() (for mixing ktime_get_real() into the
pools). However, the call to boot_init_stack_canary() for stack canary
initialization runs earlier, which triggers a warning at boot:

random: get_random_bytes called from start_kernel+0x357/0x548 with crng_init=0

Instead, this moves rand_initialize() to after timekeeping_init(), and moves
canary initialization here as well.

Note that this warning may still remain for machines that do not have
UEFI RNG support (which initializes the RNG pools during setup_arch()),
or for x86 machines without RDRAND (or booting without "random.trust=on"
or CONFIG_RANDOM_TRUST_CPU=y).

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Kees Cook 2019-04-19 23:27:05 -04:00 committed by Theodore Ts'o
parent eb9d1bf079
commit d55535232c
3 changed files with 17 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/char/random.c
View File

@ -1783,7 +1783,7 @@ EXPORT_SYMBOL(get_random_bytes_arch);
* data into the pool to prepare it for use. The pool is not cleared
* as that can only decrease the entropy in the pool.
*/
static void init_std_data(struct entropy_store *r)
static void __init init_std_data(struct entropy_store *r)
{
int i;
ktime_t now = ktime_get_real();
@ -1810,7 +1810,7 @@ static void init_std_data(struct entropy_store *r)
* take care not to overwrite the precious per platform data
* we were given.
*/
static int rand_initialize(void)
int __init rand_initialize(void)
{
init_std_data(&input_pool);
init_std_data(&blocking_pool);
@ -1822,7 +1822,6 @@ static int rand_initialize(void)
}
return 0;
}
early_initcall(rand_initialize);
#ifdef CONFIG_BLOCK
void rand_initialize_disk(struct gendisk *disk)

1
include/linux/random.h
View File

@ -36,6 +36,7 @@ extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy;
extern void get_random_bytes(void *buf, int nbytes);
extern int wait_for_random_bytes(void);
extern int __init rand_initialize(void);
extern bool rng_is_initialized(void);
extern int add_random_ready_callback(struct random_ready_callback *rdy);
extern void del_random_ready_callback(struct random_ready_callback *rdy);

21
init/main.c
View File

@ -564,13 +564,6 @@ asmlinkage __visible void __init start_kernel(void)
page_address_init();
pr_notice("%s", linux_banner);
setup_arch(&command_line);
/*
* Set up the the initial canary and entropy after arch
* and after adding latent and command line entropy.
*/
add_latent_entropy();
add_device_randomness(command_line, strlen(command_line));
boot_init_stack_canary();
mm_init_cpumask(&init_mm);
setup_command_line(command_line);
setup_nr_cpu_ids();
@ -655,6 +648,20 @@ asmlinkage __visible void __init start_kernel(void)
hrtimers_init();
softirq_init();
timekeeping_init();
/*
* For best initial stack canary entropy, prepare it after:
* - setup_arch() for any UEFI RNG entropy and boot cmdline access
* - timekeeping_init() for ktime entropy used in rand_initialize()
* - rand_initialize() to get any arch-specific entropy like RDRAND
* - add_latent_entropy() to get any latent entropy
* - adding command line entropy
*/
rand_initialize();
add_latent_entropy();
add_device_randomness(command_line, strlen(command_line));
boot_init_stack_canary();
time_init();
printk_safe_init();
perf_event_init();