Commit 58be0106 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

random: fix soft lockup when trying to read from an uninitialized blocking pool 



Fixes: eb9d1bf0: "random: only read from /dev/random after its pool has received 128 bits"
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent b7d5dc21

drivers/char/random.c

+13 −3
Original line number Diff line number Diff line
@@ -772,8 +772,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) 
	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)

		goto retry;



	if (has_initialized)

	if (has_initialized) {

		r->initialized = 1;

		wake_up_interruptible(&random_read_wait);

		kill_fasync(&fasync, SIGIO, POLL_IN);

	}



	trace_credit_entropy_bits(r->name, nbits,

				  entropy_count >> ENTROPY_SHIFT, _RET_IP_);
@@ -789,6 +792,13 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) 
			entropy_bits = r->entropy_count >> ENTROPY_SHIFT;

		}



		/* initialize the blocking pool if necessary */

		if (entropy_bits >= random_read_wakeup_bits &&

		    !other->initialized) {

			schedule_work(&other->push_work);

			return;

		}



		/* should we wake readers? */

		if (entropy_bits >= random_read_wakeup_bits &&

		    wq_has_sleeper(&random_read_wait)) {
@@ -1936,8 +1946,8 @@ _random_read(int nonblock, char __user *buf, size_t nbytes) 
			return -EAGAIN;



		wait_event_interruptible(random_read_wait,

			ENTROPY_BITS(&input_pool) >=

			random_read_wakeup_bits);

		    blocking_pool.initialized &&

		    (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits));

		if (signal_pending(current))

			return -ERESTARTSYS;

	}