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Subject[PATCH 4.19 019/234] random: Add a urandom_read_nowait() for random APIs that dont warn
Date
From: Andy Lutomirski <luto@kernel.org>

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@kernel.org>
Link: https://lore.kernel.org/r/c87ab200588de746431d9f916501ef11e5242b13.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/random.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -2025,11 +2025,22 @@ 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--;
@@ -2041,10 +2052,8 @@ 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 __poll_t
@@ -2204,7 +2213,7 @@ 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);
}

/********************************************************************

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