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lib/randutils: Do not block on getrandom() 

In Endless we have hit a problem when using 'sfdisk' on the really first
boot to automatically expand the rootfs partition. On this platform
'sfdisk' is blocking on getrandom() because not enough random bytes are
available. This is an ARM platform without a hwrng.

We fix this passing GRND_NONBLOCK to getrandom(). 'sfdisk' will use the
best entropy it has available and fallback only as necessary.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
This commit is contained in:
Carlo Caione 2018-03-19 10:31:07 +00:00 committed by Karel Zak
parent 655776a2c1
commit a9cf659e05
1 changed files with 5 additions and 1 deletions
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6
lib/randutils.c
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@ -36,6 +36,8 @@
#if !defined(HAVE_GETRANDOM) && defined(SYS_getrandom)
/* libc without function, but we have syscal */
#define GRND_NONBLOCK 0x01
#define GRND_RANDOM 0x02
static int getrandom(void *buf, size_t buflen, unsigned int flags)
{
return (syscall(SYS_getrandom, buf, buflen, flags));
@ -104,13 +106,15 @@ void random_get_bytes(void *buf, size_t nbytes)
int x;
errno = 0;
x = getrandom(cp, n, 0);
x = getrandom(cp, n, GRND_NONBLOCK);
if (x > 0) { /* success */
n -= x;
cp += x;
lose_counter = 0;
} else if (errno == ENOSYS) /* kernel without getrandom() */
break;
else if (errno == EAGAIN)
break;
else if (lose_counter++ > 16) /* entropy problem? */
break;
}