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selftests/bpf: Add test for bpf_timer overwriting crash

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[ Upstream commit a7e75016a0 ]

Add a test that validates that timer value is not overwritten when doing
a copy_map_value call in the kernel. Without the prior fix, this test
triggers a crash.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220209070324.1093182-3-memxor@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-02-09 12:33:24 +05:30 committed by Greg Kroah-Hartman
parent dc1c2b47b5
commit 4fb9be675b
2 changed files with 86 additions and 0 deletions
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32
tools/testing/selftests/bpf/prog_tests/timer_crash.c Normal file
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@ -0,0 +1,32 @@
// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
#include "timer_crash.skel.h"
enum {
MODE_ARRAY,
MODE_HASH,
};
static void test_timer_crash_mode(int mode)
{
struct timer_crash *skel;
skel = timer_crash__open_and_load();
if (!ASSERT_OK_PTR(skel, "timer_crash__open_and_load"))
return;
skel->bss->pid = getpid();
skel->bss->crash_map = mode;
if (!ASSERT_OK(timer_crash__attach(skel), "timer_crash__attach"))
goto end;
usleep(1);
end:
timer_crash__destroy(skel);
}
void test_timer_crash(void)
{
if (test__start_subtest("array"))
test_timer_crash_mode(MODE_ARRAY);
if (test__start_subtest("hash"))
test_timer_crash_mode(MODE_HASH);
}

54
tools/testing/selftests/bpf/progs/timer_crash.c Normal file
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@ -0,0 +1,54 @@
// SPDX-License-Identifier: GPL-2.0
#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_helpers.h>
struct map_elem {
struct bpf_timer timer;
struct bpf_spin_lock lock;
};
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 1);
__type(key, int);
__type(value, struct map_elem);
} amap SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1);
__type(key, int);
__type(value, struct map_elem);
} hmap SEC(".maps");
int pid = 0;
int crash_map = 0; /* 0 for amap, 1 for hmap */
SEC("fentry/do_nanosleep")
int sys_enter(void *ctx)
{
struct map_elem *e, value = {};
void *map = crash_map ? (void *)&hmap : (void *)&amap;
if (bpf_get_current_task_btf()->tgid != pid)
return 0;
*(void **)&value = (void *)0xdeadcaf3;
bpf_map_update_elem(map, &(int){0}, &value, 0);
/* For array map, doing bpf_map_update_elem will do a
* check_and_free_timer_in_array, which will trigger the crash if timer
* pointer was overwritten, for hmap we need to use bpf_timer_cancel.
*/
if (crash_map == 1) {
e = bpf_map_lookup_elem(map, &(int){0});
if (!e)
return 0;
bpf_timer_cancel(&e->timer);
}
return 0;
}
char _license[] SEC("license") = "GPL";