Add a regression test for bpf_d_path() to cover incorrect verifier assumptions caused by an incorrect function prototype. The test attaches to the fallocate hook, calls bpf_d_path() and verifies that a simple prefix comparison on the returned pathname behaves correctly after the fix in patch 1. It ensures the verifier does not assume the buffer remains unwritten.
Co-developed-by: Zesen Liu <[email protected]> Signed-off-by: Zesen Liu <[email protected]> Co-developed-by: Peili Gao <[email protected]> Signed-off-by: Peili Gao <[email protected]> Co-developed-by: Haoran Ni <[email protected]> Signed-off-by: Haoran Ni <[email protected]> Signed-off-by: Shuran Liu <[email protected]> --- .../testing/selftests/bpf/prog_tests/d_path.c | 91 +++++++++++++++---- .../testing/selftests/bpf/progs/test_d_path.c | 23 +++++ 2 files changed, 96 insertions(+), 18 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c index ccc768592e66..1a2a2f1abf03 100644 --- a/tools/testing/selftests/bpf/prog_tests/d_path.c +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c @@ -38,6 +38,14 @@ static int set_pathname(int fd, pid_t pid) return readlink(buf, src.paths[src.cnt++], MAX_PATH_LEN); } +static inline long syscall_close(int fd) +{ + return syscall(__NR_close_range, + (unsigned int)fd, + (unsigned int)fd, + 0u); +} + static int trigger_fstat_events(pid_t pid) { int sockfd = -1, procfd = -1, devfd = -1; @@ -104,36 +112,47 @@ static int trigger_fstat_events(pid_t pid) /* sys_close no longer triggers filp_close, but we can * call sys_close_range instead which still does */ -#define close(fd) syscall(__NR_close_range, fd, fd, 0) - - close(pipefd[0]); - close(pipefd[1]); - close(sockfd); - close(procfd); - close(devfd); - close(localfd); - close(indicatorfd); - -#undef close + syscall_close(pipefd[0]); + syscall_close(pipefd[1]); + syscall_close(sockfd); + syscall_close(procfd); + syscall_close(devfd); + syscall_close(localfd); + syscall_close(indicatorfd); return ret; } +static void attach_and_load(struct test_d_path **skel) +{ + int err; + + *skel = test_d_path__open_and_load(); + if (CHECK(!*skel, "setup", "d_path skeleton failed\n")) + goto cleanup; + + err = test_d_path__attach(*skel); + if (CHECK(err, "setup", "attach failed: %d\n", err)) + goto cleanup; + + (*skel)->bss->my_pid = getpid(); + return; + +cleanup: + test_d_path__destroy(*skel); + *skel = NULL; +} + static void test_d_path_basic(void) { struct test_d_path__bss *bss; struct test_d_path *skel; int err; - skel = test_d_path__open_and_load(); - if (CHECK(!skel, "setup", "d_path skeleton failed\n")) - goto cleanup; - - err = test_d_path__attach(skel); - if (CHECK(err, "setup", "attach failed: %d\n", err)) + attach_and_load(&skel); + if (!skel) goto cleanup; bss = skel->bss; - bss->my_pid = getpid(); err = trigger_fstat_events(bss->my_pid); if (err < 0) @@ -195,6 +214,39 @@ static void test_d_path_check_types(void) test_d_path_check_types__destroy(skel); } +/* Check if the verifier correctly generates code for + * accessing the memory modified by d_path helper. + */ +static void test_d_path_mem_access(void) +{ + int localfd = -1; + char path_template[] = "/dev/shm/d_path_loadgen.XXXXXX"; + struct test_d_path__bss *bss; + struct test_d_path *skel; + + attach_and_load(&skel); + if (!skel) + goto cleanup; + + bss = skel->bss; + + localfd = mkstemp(path_template); + if (CHECK(localfd < 0, "trigger", "mkstemp failed\n")) + goto cleanup; + + if (CHECK(fallocate(localfd, 0, 0, 1024) < 0, "trigger", "fallocate failed\n")) + goto cleanup; + remove(path_template); + + if (CHECK(!bss->path_match_fallocate, "check", + "failed to read fallocate path")) + goto cleanup; + +cleanup: + syscall_close(localfd); + test_d_path__destroy(skel); +} + void test_d_path(void) { if (test__start_subtest("basic")) @@ -205,4 +257,7 @@ void test_d_path(void) if (test__start_subtest("check_alloc_mem")) test_d_path_check_types(); + + if (test__start_subtest("check_mem_access")) + test_d_path_mem_access(); } diff --git a/tools/testing/selftests/bpf/progs/test_d_path.c b/tools/testing/selftests/bpf/progs/test_d_path.c index 84e1f883f97b..561b2f861808 100644 --- a/tools/testing/selftests/bpf/progs/test_d_path.c +++ b/tools/testing/selftests/bpf/progs/test_d_path.c @@ -17,6 +17,7 @@ int rets_close[MAX_FILES] = {}; int called_stat = 0; int called_close = 0; +int path_match_fallocate = 0; SEC("fentry/security_inode_getattr") int BPF_PROG(prog_stat, struct path *path, struct kstat *stat, @@ -62,4 +63,26 @@ int BPF_PROG(prog_close, struct file *file, void *id) return 0; } +SEC("fentry/vfs_fallocate") +int BPF_PROG(prog_fallocate, struct file *file, int mode, loff_t offset, loff_t len) +{ + pid_t pid = bpf_get_current_pid_tgid() >> 32; + int ret = 0; + char path_fallocate[MAX_PATH_LEN] = {}; + + if (pid != my_pid) + return 0; + + ret = bpf_d_path(&file->f_path, + path_fallocate, MAX_PATH_LEN); + if (ret < 0) + return 0; + + if (!path_fallocate[0]) + return 0; + + path_match_fallocate = 1; + return 0; +} + char _license[] SEC("license") = "GPL"; -- 2.52.0
