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    Subject[PATCH 4.14 031/237] random: add GRND_INSECURE to return best-effort non-cryptographic bytes
    Date
    From: Andy Lutomirski <luto@kernel.org>

    commit 75551dbf112c992bc6c99a972990b3f272247e23 upstream.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Link: https://lore.kernel.org/r/d5473b56cf1fa900ca4bd2b3fc1e5b8874399919.1577088521.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 | 11 +++++++++--
    include/uapi/linux/random.h | 2 ++
    2 files changed, 11 insertions(+), 2 deletions(-)

    --- a/drivers/char/random.c
    +++ b/drivers/char/random.c
    @@ -2134,7 +2134,14 @@ SYSCALL_DEFINE3(getrandom, char __user *
    {
    int ret;

    - if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
    + if (flags & ~(GRND_NONBLOCK|GRND_RANDOM|GRND_INSECURE))
    + return -EINVAL;
    +
    + /*
    + * Requesting insecure and blocking randomness at the same time makes
    + * no sense.
    + */
    + if ((flags & (GRND_INSECURE|GRND_RANDOM)) == (GRND_INSECURE|GRND_RANDOM))
    return -EINVAL;

    if (count > INT_MAX)
    @@ -2143,7 +2150,7 @@ SYSCALL_DEFINE3(getrandom, char __user *
    if (flags & GRND_RANDOM)
    return _random_read(flags & GRND_NONBLOCK, buf, count);

    - if (!crng_ready()) {
    + if (!(flags & GRND_INSECURE) && !crng_ready()) {
    if (flags & GRND_NONBLOCK)
    return -EAGAIN;
    ret = wait_for_random_bytes();
    --- a/include/uapi/linux/random.h
    +++ b/include/uapi/linux/random.h
    @@ -49,8 +49,10 @@ struct rand_pool_info {
    *
    * GRND_NONBLOCK Don't block and return EAGAIN instead
    * GRND_RANDOM Use the /dev/random pool instead of /dev/urandom
    + * GRND_INSECURE Return non-cryptographic random bytes
    */
    #define GRND_NONBLOCK 0x0001
    #define GRND_RANDOM 0x0002
    +#define GRND_INSECURE 0x0004

    #endif /* _UAPI_LINUX_RANDOM_H */

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