Commit 46c8229c authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'Don't reinit map value in prealloc_lru_pop' 

Kumar Kartikeya Dwivedi says:

====================

Fix for a bug in prealloc_lru_pop spotted while reading the code, then a test +
example that checks whether it is fixed.

Changelog:
----------
v2 -> v3:
v2: https://lore.kernel.org/bpf/20220809140615.21231-1-memxor@gmail.com

 * Switch test to use kptr instead of kptr_ref to stabilize test runs
 * Fix missing lru_bug__destroy (Yonghong)
 * Collect Acks

v1 -> v2:
v1: https://lore.kernel.org/bpf/20220806014603.1771-1-memxor@gmail.com



 * Expand commit log to include summary of the discussion with Yonghong
 * Make lru_bug selftest serial to not mess up refcount for map_kptr test
====================

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents 19f68ed6 de7b9927

kernel/bpf/hashtab.c

+1 −5
Original line number Diff line number Diff line
@@ -311,12 +311,8 @@ static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key, 
	struct htab_elem *l;



	if (node) {

		u32 key_size = htab->map.key_size;



		l = container_of(node, struct htab_elem, lru_node);

		memcpy(l->key, key, key_size);

		check_and_init_map_value(&htab->map,

					 l->key + round_up(key_size, 8));

		memcpy(l->key, key, htab->map.key_size);

		return l;

	}

net/bpf/test_run.c

+1 −0
Original line number Diff line number Diff line
@@ -1628,6 +1628,7 @@ static int __init bpf_prog_test_run_init(void) 
	int ret;



	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set);

	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_prog_test_kfunc_set);

	return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc,

						  ARRAY_SIZE(bpf_prog_test_dtor_kfunc),

						  THIS_MODULE);

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";