| Message ID | 20220209011919.493762-7-Jason@zx2c4.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/9] random: use RDSEED instead of RDRAND in entropy extraction | expand |
diff --git a/drivers/char/random.c b/drivers/char/random.c index 785a4545c9d7..20374bce9a07 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -864,6 +864,13 @@ void add_interrupt_randomness(int irq) crng_fast_load((u8 *)fast_pool->pool, sizeof(fast_pool->pool)) > 0) { fast_pool->count = 0; fast_pool->last = now; + + /* Technically this call means that we're using a spinlock_t + * in the IRQ handler, which isn't terrific for PREEMPT_RT. + * However, this only happens during very early boot, and then + * never again, so we live with it. + */ + mix_pool_bytes(&fast_pool->pool, sizeof(fast_pool->pool)); } return; }
During crng_init == 0, we never credit entropy in add_interrupt_ randomness(), but instead dump it directly into the base_crng. That's fine, except for the fact that we then wind up throwing away that entropy later when we switch to extracting from the input pool and overwriting the base_crng key. The two other early init sites -- add_hwgenerator_randomness()'s use crng_fast_load() and add_device_ randomness()'s use of crng_slow_load() -- always additionally give their inputs to the input pool. But not add_interrupt_randomness(). This commit fixes that shortcoming by calling mix_pool_bytes() after crng_fast_load() in add_interrupt_randomness(). That's partially verboten on PREEMPT_RT, where it implies taking spinlock_t from an IRQ handler. But this also only happens during early boot and then never again after that. Should this turn into a larger problem later for some esoteric reason, we can always use `if (IS_ENABLED(PREEMPT_RT))` or something similar to that. But for now, this should do. Cc: Theodore Ts'o <tytso@mit.edu> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Suggested-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- drivers/char/random.c | 7 +++++++ 1 file changed, 7 insertions(+)