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 <lkp@intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index a42b3d764da8..5d5ea4ce1442 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;
         }