[PATCH 4.9 054/264] random: Add a urandom_read_nowait() for random APIs that dont warn

[Greg Kroah-Hartman]

From: Andy Lutomirski <luto@xxxxxxxxxx>

commit c6f1deb158789abba02a7eba600747843eeb3a57 upstream.

/dev/random and getrandom() never warn.  Split the meat of
urandom_read() into urandom_read_nowarn() and leave the warning code
in urandom_read().

This has no effect on kernel behavior, but it makes subsequent
patches more straightforward.  It also makes the fact that
getrandom() never warns more obvious.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lore.kernel.org/r/c87ab200588de746431d9f916501ef11e5242b13.1577088521.git.luto@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/char/random.c |   21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2015,11 +2015,22 @@ random_read(struct file *file, char __us
 }
 
 static ssize_t
+urandom_read_nowarn(struct file *file, char __user *buf, size_t nbytes,
+		    loff_t *ppos)
+{
+	int ret;
+
+	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
+	ret = extract_crng_user(buf, nbytes);
+	trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
+	return ret;
+}
+
+static ssize_t
 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 {
 	unsigned long flags;
 	static int maxwarn = 10;
-	int ret;
 
 	if (!crng_ready() && maxwarn > 0) {
 		maxwarn--;
@@ -2031,10 +2042,8 @@ urandom_read(struct file *file, char __u
 		crng_init_cnt = 0;
 		spin_unlock_irqrestore(&primary_crng.lock, flags);
 	}
-	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
-	ret = extract_crng_user(buf, nbytes);
-	trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
-	return ret;
+
+	return urandom_read_nowarn(file, buf, nbytes, ppos);
 }
 
 static unsigned int
@@ -2194,7 +2203,7 @@ SYSCALL_DEFINE3(getrandom, char __user *
 		if (unlikely(ret))
 			return ret;
 	}
-	return urandom_read(NULL, buf, count, NULL);
+	return urandom_read_nowarn(NULL, buf, count, NULL);
 }
 
 /********************************************************************