On 2017-06-15 00:33:12 [+0200], Jason A. Donenfeld wrote: > There's a potential race that I fixed in my v5 of that patch set, but > Ted only took v4, and for whatever reason has been to busy to submit > the additional patch I already posted showing the diff between v4&v5. > Hopefully he actually gets around to it and sends this for the next > rc. Here it is: > > https://patchwork.kernel.org/patch/9774563/ So you replace "crng_init < 2" with use_lock instead. That is not what I am talking about. Again: add_interrupt_randomness() -> crng_fast_load() spin_trylock_irqsave(&primary_crng.lock, ) -> invalidate_batched_entropy() write_lock_irqsave(&batched_entropy_reset_lock, ); in that order while the code path get_random_uXX() read_lock_irqsave(&batched_entropy_reset_lock, ); -> extract_crng() -> _extract_crng() spin_lock_irqsave(&crng->lock, ); which allocates the same lock in opposite order. That means T1 T2 crng_fast_load() get_random_u64() extract_crng() *dead lock* invalidate_batched_entropy() _extract_crng() So T1 waits for batched_entropy_reset_lock holding primary_crng.lock and T2 waits for primary_crng.lock holding batched_entropy_reset_lock. Sebastian
