Commit 44bab87d authored by Hao Luo's avatar Hao Luo Committed by Andrii Nakryiko

bpf/selftests: Test bpf_d_path on rdonly_mem.

The second parameter of bpf_d_path() can only accept writable
memories. Rdonly_mem obtained from bpf_per_cpu_ptr() can not
be passed into bpf_d_path for modification. This patch adds
a selftest to verify this behavior.
Signed-off-by: default avatarHao Luo <haoluo@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220106205525.2116218-1-haoluo@google.com
parent e59618f0
...@@ -9,6 +9,7 @@ ...@@ -9,6 +9,7 @@
#define MAX_FILES 7 #define MAX_FILES 7
#include "test_d_path.skel.h" #include "test_d_path.skel.h"
#include "test_d_path_check_rdonly_mem.skel.h"
static int duration; static int duration;
...@@ -99,7 +100,7 @@ static int trigger_fstat_events(pid_t pid) ...@@ -99,7 +100,7 @@ static int trigger_fstat_events(pid_t pid)
return ret; return ret;
} }
void test_d_path(void) static void test_d_path_basic(void)
{ {
struct test_d_path__bss *bss; struct test_d_path__bss *bss;
struct test_d_path *skel; struct test_d_path *skel;
...@@ -155,3 +156,22 @@ void test_d_path(void) ...@@ -155,3 +156,22 @@ void test_d_path(void)
cleanup: cleanup:
test_d_path__destroy(skel); test_d_path__destroy(skel);
} }
static void test_d_path_check_rdonly_mem(void)
{
struct test_d_path_check_rdonly_mem *skel;
skel = test_d_path_check_rdonly_mem__open_and_load();
ASSERT_ERR_PTR(skel, "unexpected_load_overwriting_rdonly_mem");
test_d_path_check_rdonly_mem__destroy(skel);
}
void test_d_path(void)
{
if (test__start_subtest("basic"))
test_d_path_basic();
if (test__start_subtest("check_rdonly_mem"))
test_d_path_check_rdonly_mem();
}
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Google */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
extern const int bpf_prog_active __ksym;
SEC("fentry/security_inode_getattr")
int BPF_PROG(d_path_check_rdonly_mem, struct path *path, struct kstat *stat,
__u32 request_mask, unsigned int query_flags)
{
void *active;
__u32 cpu;
cpu = bpf_get_smp_processor_id();
active = (void *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
if (active) {
/* FAIL here! 'active' points to readonly memory. bpf helpers
* that update its arguments can not write into it.
*/
bpf_d_path(path, active, sizeof(int));
}
return 0;
}
char _license[] SEC("license") = "GPL";
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