Commit de7b9927 authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add test for prealloc_lru_pop bug 



Add a regression test to check against invalid check_and_init_map_value
call inside prealloc_lru_pop.

The kptr should not be reset to NULL once we set it after deleting the
map element. Hence, we trigger a program that updates the element
causing its reuse, and checks whether the unref kptr is reset or not.
If it is, prealloc_lru_pop does an incorrect check_and_init_map_value
call and the test fails.

Acked-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220809213033.24147-4-memxor@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 275c30bc

tools/testing/selftests/bpf/prog_tests/lru_bug.c

0 → 100644
+21 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <test_progs.h>



#include "lru_bug.skel.h"



void test_lru_bug(void)

{

	struct lru_bug *skel;

	int ret;



	skel = lru_bug__open_and_load();

	if (!ASSERT_OK_PTR(skel, "lru_bug__open_and_load"))

		return;

	ret = lru_bug__attach(skel);

	if (!ASSERT_OK(ret, "lru_bug__attach"))

		goto end;

	usleep(1);

	ASSERT_OK(skel->data->result, "prealloc_lru_pop doesn't call check_and_init_map_value");

end:

	lru_bug__destroy(skel);

}

tools/testing/selftests/bpf/progs/lru_bug.c

0 → 100644
+49 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_helpers.h>



struct map_value {

	struct task_struct __kptr *ptr;

};



struct {

	__uint(type, BPF_MAP_TYPE_LRU_HASH);

	__uint(max_entries, 1);

	__type(key, int);

	__type(value, struct map_value);

} lru_map SEC(".maps");



int pid = 0;

int result = 1;



SEC("fentry/bpf_ktime_get_ns")

int printk(void *ctx)

{

	struct map_value v = {};



	if (pid == bpf_get_current_task_btf()->pid)

		bpf_map_update_elem(&lru_map, &(int){0}, &v, 0);

	return 0;

}



SEC("fentry/do_nanosleep")

int nanosleep(void *ctx)

{

	struct map_value val = {}, *v;

	struct task_struct *current;



	bpf_map_update_elem(&lru_map, &(int){0}, &val, 0);

	v = bpf_map_lookup_elem(&lru_map, &(int){0});

	if (!v)

		return 0;

	bpf_map_delete_elem(&lru_map, &(int){0});

	current = bpf_get_current_task_btf();

	v->ptr = current;

	pid = current->pid;

	bpf_ktime_get_ns();

	result = !v->ptr;

	return 0;

}



char _license[] SEC("license") = "GPL";