getrandom never-ending busy-loop

[bagder]

In this curl issue, someone uses c-ares in a system where getrandom returns -1 with errno set to ENOSYS. It makes c-ares get stuck in a never-ending loop here:

c-ares/src/lib/ares_rand.c

Lines 274 to 282 in 290e9e9

	while (1) {
	size_t n = len - bytes_read;
	/* getrandom() on Linux always succeeds and is never
	* interrupted by a signal when requesting <= 256 bytes.
	*/
	ssize_t rv = getrandom(buf + bytes_read, n > 256 ? 256 : n, 0);
	if (rv <= 0) {
	continue; /* Just retry. */
	}

[bradh352]

Interesting that the system would have getrandom but the kernel not support it. We can implement a fallback for this case.

[bradh352]

fixed in #661