On Thu, Oct 13, 2022 at 10:32:31AM -0600, Jason A. Donenfeld wrote:
> commit cd4f24ae9404fd31fc461066e57889be3b68641b upstream.
>
> Prior to 5.6, when /dev/random was opened with O_NONBLOCK, it would
> return -EAGAIN if there was no entropy. When the pools were unified in
> 5.6, this was lost. The post 5.6 behavior of blocking until the pool is
> initialized, and ignoring O_NONBLOCK in the process, went unnoticed,
> with no reports about the regression received for two and a half years.
> However, eventually this indeed did break somebody's userspace.
>
> So we restore the old behavior, by returning -EAGAIN if the pool is not
> initialized. Unlike the old /dev/random, this can only occur during
> early boot, after which it never blocks again.
>
> In order to make this O_NONBLOCK behavior consistent with other
> expectations, also respect users reading with preadv2(RWF_NOWAIT) and
> similar.
>
> Fixes: 30c08efec888 ("random: make /dev/random be almost like /dev/urandom")
> Reported-by: Guozihua <guozihua@xxxxxxxxxx>
> Reported-by: Zhongguohua <zhongguohua1@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Cc: Andrew Lutomirski <luto@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> ---
> drivers/char/random.c | 4 ++++
> 1 file changed, 4 insertions(+)
Now queued up, thanks.
greg k-h
