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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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