APPLIED: [SRU bionic] random: Make getrandom() ready earlier

[Kleber Souza]

On 07/04/18 16:15, Stefan Bader wrote:
> From: Ben Hutchings <ben at decadent.org.uk>
> 
> This effectively reverts commit 725e828 "random: fix crng_ready()
> test" which was commit 43838a23a05f upstream.  Unfortunately some
> users of getrandom() don't expect it to block for long, and they need
> to be fixed before we can allow this change into stable.
> 
> This doesn't directly revert that commit, but only weakens the ready
> condition used by getrandom() when the GRND_RANDOM flag is not set.
> Calls to getrandom() that return before the RNG is fully seeded will
> generate warnings, just like reads from /dev/urandom.
> 
> https://bugs.launchpad.net/bugs/1780062
> 
> (backported from ://salsa.debian.org/kernel-team/linux/raw/stretch/debian/patches/debian/random-make-getrandom-ready-earlier.patch)
> [smb: open code waiting in getrandom directly]
> Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
> ---
> This is based on the patch from Ben Hutchings in Debian. But since
> wait_for_random_bytes, which is used in the 4.15 code is exported
> and used by other things, I did instead do its own wait in getrandom().
> 
> -Stefan
> 
>  drivers/char/random.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index d5f1211..6021405 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -1976,10 +1976,10 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
>  	if (flags & GRND_RANDOM)
>  		return _random_read(flags & GRND_NONBLOCK, buf, count);
>  
> -	if (!crng_ready()) {
> +	if (crng_init == 0) {
>  		if (flags & GRND_NONBLOCK)
>  			return -EAGAIN;
> -		ret = wait_for_random_bytes();
> +		ret = wait_event_interruptible(crng_init_wait, crng_init > 0);
>  		if (unlikely(ret))
>  			return ret;
>  	}
> 

This patch has been applied to bionic/master-next branch.

Thanks,
Kleber