On Tue 08-01-19 17:46:07, Jan Kara wrote:
> Hello,
>
> When waiting for response to fanotify permission events, we currently use
> uninterruptible waits. That makes code simple however it can cause lots of
> processes to end up in uninterruptible sleep with hard reboot being the only
> alternative in case fanotify listener process stops responding (e.g. due to a
> bug in its implementation) - reported e.g. in [1]. Uninterruptible sleep also
> makes system hibernation fail if the listener gets frozen before the process
> generating fanotify permission event (as reported e.g. here [2]).
>
> This patch set modifies fanotify so that it will use interruptible wait when
> waiting for fanotify permission event response. Patches are based on current
> Linus' tree for the ease of testing (I plan to rebase them on top of Amir's
> pending changes later). I have also create LTP test which stresses handling of
> permission events while sending processes signals to test the new code - I'll
> send that separately later. Review, comments, and testing are welcome.
>
> [1] https://lore.kernel.org/lkml/153474898224.6806.12518115530793064797.stgit@buzz/
> [2] https://lore.kernel.org/lkml/c1bb16b7-9eee-9cea-2c96-a512d8b3b9c7@xxxxxxxx/
>
Patch adding LTP test I have created for excercising new code is attached.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
>From 53bdff3951596f8084127998c085d4ff94667873 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 8 Jan 2019 17:01:40 +0100
Subject: [PATCH] syscalls/fanotify12: New test to test signal handling for
permission events
Test whether kernel survives when processes waiting for response to
fanotify permission event are interrupted by a signal.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
testcases/kernel/syscalls/fanotify/.gitignore | 1 +
testcases/kernel/syscalls/fanotify/fanotify12.c | 217 ++++++++++++++++++++++++
2 files changed, 218 insertions(+)
create mode 100644 testcases/kernel/syscalls/fanotify/fanotify12.c
diff --git a/testcases/kernel/syscalls/fanotify/.gitignore b/testcases/kernel/syscalls/fanotify/.gitignore
index 3818e241ffcf..d583d459b4aa 100644
--- a/testcases/kernel/syscalls/fanotify/.gitignore
+++ b/testcases/kernel/syscalls/fanotify/.gitignore
@@ -9,3 +9,4 @@
/fanotify09
/fanotify10
/fanotify11
+/fanotify12
diff --git a/testcases/kernel/syscalls/fanotify/fanotify12.c b/testcases/kernel/syscalls/fanotify/fanotify12.c
new file mode 100644
index 000000000000..462c85031c0b
--- /dev/null
+++ b/testcases/kernel/syscalls/fanotify/fanotify12.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2019 SUSE. All Rights Reserved.
+ *
+ * Started by Jan Kara <jack@xxxxxxx>
+ *
+ * DESCRIPTION
+ * Check how fanotify permission events deal with signals.
+ */
+#define _GNU_SOURCE
+#include "config.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/fcntl.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/syscall.h>
+#include "tst_test.h"
+#include "lapi/syscalls.h"
+#include "fanotify.h"
+
+#if defined(HAVE_SYS_FANOTIFY_H)
+#include <sys/fanotify.h>
+
+#define BUF_SIZE 256
+static char fname[BUF_SIZE];
+static char buf[BUF_SIZE];
+static volatile int fd_notify;
+
+/* Number of children we start */
+#define MAX_CHILDREN 16
+static pid_t child_pid[MAX_CHILDREN];
+
+/* Number of events we process before stopping */
+#define MAX_EVENTS 10000
+
+static void generate_events(void)
+{
+ int fd;
+
+ /*
+ * generate sequence of events
+ */
+ if ((fd = open(fname, O_RDWR | O_CREAT, 0700)) == -1)
+ exit(1);
+
+ /* Run until killed... */
+ while (1) {
+ lseek(fd, 0, SEEK_SET);
+ if (read(fd, buf, BUF_SIZE) == -1)
+ exit(3);
+ }
+}
+
+static void usrhandler(int sig)
+{
+ /* Do nothing */
+}
+
+static void send_signals(void)
+{
+ while (1) {
+ usleep(random() % 200);
+ SAFE_KILL(child_pid[random() % (MAX_CHILDREN-1)], SIGUSR1);
+ }
+}
+
+static void run_children(void)
+{
+ int i;
+
+ for (i = 0; i < MAX_CHILDREN; i++) {
+ child_pid[i] = SAFE_FORK();
+ if (!child_pid[i]) {
+ /* Child will generate events now */
+ close(fd_notify);
+ if (i == MAX_CHILDREN - 1) {
+ send_signals();
+ } else {
+ SAFE_SIGNAL(SIGUSR1, usrhandler);
+ generate_events();
+ }
+ exit(0);
+ }
+ }
+}
+
+static int stop_children(void)
+{
+ int child_ret;
+ int i, ret = 0;
+
+ for (i = 0; i < MAX_CHILDREN; i++)
+ SAFE_KILL(child_pid[i], SIGKILL);
+
+ for (i = 0; i < MAX_CHILDREN; i++) {
+ SAFE_WAITPID(child_pid[i], &child_ret, 0);
+ if (!WIFSIGNALED(child_ret))
+ ret = 1;
+ }
+
+ return ret;
+}
+
+static int setup_instance(void)
+{
+ int fd;
+
+ fd = SAFE_FANOTIFY_INIT(FAN_CLASS_CONTENT, O_RDONLY);
+
+ if (fanotify_mark(fd, FAN_MARK_ADD, FAN_ACCESS_PERM, AT_FDCWD,
+ fname) < 0) {
+ close(fd);
+ if (errno == EINVAL) {
+ tst_brk(TCONF | TERRNO,
+ "CONFIG_FANOTIFY_ACCESS_PERMISSIONS not "
+ "configured in kernel?");
+ } else {
+ tst_brk(TBROK | TERRNO,
+ "fanotify_mark (%d, FAN_MARK_ADD, FAN_ACCESS_PERM, "
+ "AT_FDCWD, %s) failed.", fd, fname);
+ }
+ }
+
+ return fd;
+}
+
+static void handle_fanotify_events(void)
+{
+ int events = 0;
+
+ /*
+ * check events
+ */
+ while (events < MAX_EVENTS) {
+ struct fanotify_event_metadata event;
+ struct fanotify_response resp;
+
+ /* Sleep randomly to give time for signal to be delivered */
+ usleep(random() % 1000);
+
+ /* Get more events */
+ SAFE_READ(1, fd_notify, &event, sizeof(event));
+
+ if (event.mask != FAN_ACCESS_PERM) {
+ tst_res(TFAIL,
+ "got event: mask=%llx (expected %llx) "
+ "pid=%u fd=%d",
+ (unsigned long long)event.mask,
+ (unsigned long long)FAN_ACCESS_PERM,
+ (unsigned)event.pid, event.fd);
+ break;
+ }
+
+ /* Sleep randomly to give time for signal to be delivered */
+ usleep(random() % 1000);
+ /* Write response to permission event */
+ resp.fd = event.fd;
+ resp.response = FAN_ALLOW;
+ SAFE_WRITE(1, fd_notify, &resp, sizeof(resp));
+ SAFE_CLOSE(event.fd);
+ events++;
+ }
+}
+
+static void test_fanotify(void)
+{
+ int ret;
+
+ fd_notify = setup_instance();
+ run_children();
+ handle_fanotify_events();
+
+ /*
+ * Now destroy the fanotify instance while there are permission
+ * events at various stages of processing. This may provoke
+ * kernel hangs or crashes.
+ */
+ SAFE_CLOSE(fd_notify);
+
+ ret = stop_children();
+ if (ret)
+ tst_res(TFAIL, "child exited for unexpected reason");
+ else
+ tst_res(TPASS, "all children exited successfully");
+}
+
+static void setup(void)
+{
+ sprintf(fname, "fname_%d", getpid());
+ SAFE_FILE_PRINTF(fname, "%s", fname);
+}
+
+static void cleanup(void)
+{
+ if (fd_notify > 0)
+ SAFE_CLOSE(fd_notify);
+}
+
+static struct tst_test test = {
+ .test_all = test_fanotify,
+ .setup = setup,
+ .cleanup = cleanup,
+ .needs_tmpdir = 1,
+ .forks_child = 1,
+ .needs_root = 1,
+};
+
+#else
+ TST_TEST_TCONF("system doesn't have required fanotify support");
+#endif
--
2.16.4
