[PATCH v3 2/8] random: Add a urandom_read_nowait() for random APIs that don't warn

Andy Lutomirski
2019-12-23T08:21:42Z

/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@kernel.org>
---
drivers/char/random.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index c6252a3a4aec..7b46751772e5 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2018,12 +2018,23 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
}

+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--;
@@ -2035,10 +2046,8 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
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 __poll_t
@@ -2200,7 +2209,7 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
if (unlikely(ret))
return ret;
}
- return urandom_read(NULL, buf, count, NULL);
+ return urandom_read_nowarn(NULL, buf, count, NULL);
}

/********************************************************************
--
2.23.0