repro_access_to_stack_error_bpf

Makefile

.PHONY: repro
repro:
	$(CLANG) -Wall -Wextra -O2 --target=bpf -c -g \
		repro.bpf.c \
		-o repro.bpf.o
	bpftool gen skeleton repro.bpf.o > repro.bpf.skel.h
	$(CLANG) -Wall -fno-omit-frame-pointer -Wextra -O2 -g \
		repro.c \
		-lbpf \
		-lelf \
		-lz \
		-o repro

repro.bpf.c

#include <stddef.h>
#include <string.h>
#include <linux/types.h>

#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
#include <linux/bpf.h>

struct {
	__uint(type, BPF_MAP_TYPE_RINGBUF);
	__uint(max_entries, 4 * 1024);
} rb SEC(".maps");

struct event {
	__u64 this_field_works_with_u32_fails_with_u64;
	char v6[16];
};

SEC("sockops")
int bpf_testcb(struct bpf_sock_ops *skops)
{
	struct event e = {};
	memcpy(&e.v6, &skops->remote_ip6, 16);

	bpf_ringbuf_output(&rb, &e, sizeof(e), 0);
	return 1;
}

repro.c

#include <errno.h>
#include <error.h>
#include <stdio.h>

#include "repro.bpf.skel.h"

int main()
{
	struct repro_bpf *skel = repro_bpf__open_and_load();
	if (!skel) {
		error(1, errno, "Failed to open and load BPF skeleton\n");
	}
}

Solution:

static void u32_memcpy(void *dest, void *src, size_t n){
	__u32 *d = dest;
	__u32 *s = src;
	size_t o = 0;

	while (o < n/4) {
		d[o] = s[o];
		o += 1;
	}
	o*=4;
	if (n - o > 0) {
		__builtin_memcpy(d+o, s+o, n-o);
	}
}