From 643e160210dbeadf161c1dd122604e1115b79927 Mon Sep 17 00:00:00 2001 From: Bhavik Sachdev Date: Thu, 25 Jul 2024 01:12:36 +0530 Subject: [PATCH] zdtm: Check dead pidfd is restored correctly After, C/R of pidfds that point to dead processes their inodes might change. But if two pidfds point to same dead process they should continue to do so after C/R. This test ensures that this happens by calling `statx()` on pidfds after C/R and then comparing their inode numbers. Support for comparing pidfds by using `statx()` and inode numbers was introduced alongside pidfs. So if `f_type` of pidfd is not equal to `PID_FS_MAGIC` then we skip this test. signed-off-by: Bhavik Sachdev --- test/zdtm/static/Makefile | 1 + test/zdtm/static/pidfd_dead.c | 244 ++++++++++++++++++++++++++++++++++ 2 files changed, 245 insertions(+) create mode 100644 test/zdtm/static/pidfd_dead.c diff --git a/test/zdtm/static/Makefile b/test/zdtm/static/Makefile index ab45b580a..20e4bc272 100644 --- a/test/zdtm/static/Makefile +++ b/test/zdtm/static/Makefile @@ -54,6 +54,7 @@ TST_NOFILE := \ shm-mp \ ptrace_sig \ pidfd_self \ + pidfd_dead \ pidfd_child \ pidfd_kill \ pipe00 \ diff --git a/test/zdtm/static/pidfd_dead.c b/test/zdtm/static/pidfd_dead.c new file mode 100644 index 000000000..9c825899d --- /dev/null +++ b/test/zdtm/static/pidfd_dead.c @@ -0,0 +1,244 @@ +#include +#include +#include +#include +#include +#include + +#include "zdtmtst.h" + +const char *test_doc = "Check C/R of pidfds that point to dead processes\n"; +const char *test_author = "Bhavik Sachdev "; + +#ifndef PID_FS_MAGIC +#define PID_FS_MAGIC 0x50494446 +#endif + +/* + * main + * `- child + * `- grandchild + * + * main opens a pidfd for both child and grandchild. + * Before C/R we kill both child and grandchild. + * We end up with two unique dead pidfds. + */ + +static long get_fs_type(int lfd) +{ + struct statfs fst; + + if (fstatfs(lfd, &fst)) { + return -1; + } + return fst.f_type; +} + +static int pidfd_open(pid_t pid, unsigned int flags) +{ + return syscall(__NR_pidfd_open, pid, flags); +} + +static int pidfd_send_signal(int pidfd, int sig, siginfo_t* info, unsigned int flags) +{ + return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags); +} + +static int open_pidfd_pair(int pidfd[2], int pid) +{ + pidfd[0] = pidfd_open(pid, 0); + if (pidfd[0] < 0) { + pr_perror("pidfd_open() failed"); + return 1; + } + + pidfd[1] = pidfd_open(pid, 0); + if (pidfd[1] < 0) { + close(pidfd[0]); + pr_perror("pidfd_open() failed"); + return 1; + } + return 0; +} + +static int compare_pidfds(int pidfd[2]) +{ + /* + * After linux 6.9 we can compare inode numbers + * to determine if two pidfds point to the same process. + * While the inode number may change before and after C/R + * pidfds pointing to the same pid should have the same inode number. + */ + struct statx stats[2]; + statx(pidfd[0], "", AT_EMPTY_PATH, STATX_ALL, &stats[0]); + statx(pidfd[1], "", AT_EMPTY_PATH, STATX_ALL, &stats[1]); + if (stats[0].stx_ino != stats[1].stx_ino) + return 1; + return 0; +} + +static int check_for_pidfs(void) +{ + long type; + int pidfd = pidfd_open(getpid(), 0); + if (pidfd < 0) { + pr_perror("pidfd open() failed"); + return -1; + } + type = get_fs_type(pidfd); + close(pidfd); + return type == PID_FS_MAGIC; +} + +int main(int argc, char* argv[]) +{ + #define READ 0 + #define WRITE 1 + + int child, ret, gchild, p[2], status; + int cpidfd[2], gpidfd[2]; + struct statx stats[2]; + + test_init(argc, argv); + + ret = check_for_pidfs(); + if (ret < 0) + return 1; + + if (ret == 0) { + test_daemon(); + test_waitsig(); + skip("Test requires pidfs. skipping..."); + pass(); + return 0; + } + + if (pipe(p)) { + pr_perror("pipe"); + return 1; + } + + child = test_fork(); + if (child < 0) { + pr_perror("fork"); + return 1; + } else if (child == 0) { + int gchild = test_fork(); + close(p[READ]); + if (gchild < 0) { + pr_perror("fork"); + return 1; + } else if (gchild == 0) { + close(p[WRITE]); + while(1) + sleep(1000); + } else { + if (write(p[WRITE], &gchild, sizeof(int)) != sizeof(int)) { + pr_perror("write"); + return 1; + } + close(p[WRITE]); + if (waitpid(gchild, &status, 0) != gchild) { + pr_perror("waitpid"); + return 1; + } + + if (!WIFSIGNALED(status)) { + fail("Expected grandchild to be terminated by a signal"); + return 1; + } + + if (WTERMSIG(status) != SIGKILL) { + fail("Expected grandchild to be terminated by SIGKILL"); + return 1; + } + + return 0; + } + } + + ret = open_pidfd_pair(cpidfd, child); + if (ret) + return 1; + + close(p[WRITE]); + if (read(p[READ], &gchild, sizeof(int)) != sizeof(int)) { + pr_perror("write"); + return 1; + } + close(p[READ]); + + ret = open_pidfd_pair(gpidfd, gchild); + if (ret) + return 1; + + /* + * We kill grandchild and child processes only after opening pidfds. + */ + if (pidfd_send_signal(gpidfd[0], SIGKILL, NULL, 0)) { + pr_perror("pidfd_send_signal"); + goto fail_close; + } + + if (waitpid(child, &status, 0) != child) { + pr_perror("waitpid"); + goto fail_close; + } + + if (!WIFEXITED(status)) { + fail("Expected child to exit normally"); + goto fail_close; + } + + if (WEXITSTATUS(status) != 0) { + fail("Expected child to exit with 0"); + goto fail_close; + } + usleep(1000); + + if (kill(gchild, 0) != -1 && errno != ESRCH) { + fail("Expected grand child to not exist"); + goto fail_close; + } + + if (kill(child, 0) != -1 && errno != ESRCH) { + fail("Expected child to not exist"); + goto fail_close; + } + + test_daemon(); + test_waitsig(); + + ret = compare_pidfds(cpidfd); + if (ret) { + fail("inodes not same for same pid"); + goto fail_close; + } + + ret = compare_pidfds(gpidfd); + if (ret) { + fail("inodes not same for same pid"); + goto fail_close; + } + + statx(cpidfd[0], "", AT_EMPTY_PATH, STATX_ALL, &stats[0]); + statx(gpidfd[0], "", AT_EMPTY_PATH, STATX_ALL, &stats[1]); + if (stats[0].stx_ino == stats[1].stx_ino) { + fail("pidfds pointing to diff pids should have diff inodes"); + goto fail_close; + } + + pass(); + close(cpidfd[0]); + close(cpidfd[1]); + close(gpidfd[0]); + close(gpidfd[1]); + return 0; + +fail_close: + close(cpidfd[0]); + close(cpidfd[1]); + close(gpidfd[0]); + close(gpidfd[1]); + return 1; +}