From 58be0106c5306b939b07b4b8bf00669a20593f4b Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 22 May 2019 12:02:16 -0400 Subject: [PATCH] random: fix soft lockup when trying to read from an uninitialized blocking pool Fixes: eb9d1bf079bb: "random: only read from /dev/random after its pool has received 128 bits" Reported-by: kernel test robot Signed-off-by: Theodore Ts'o --- drivers/char/random.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index a42b3d7..5d5ea4c 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -772,8 +772,11 @@ retry: 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 @@ retry: 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; } -- 2.7.4