fanotify: Add test for permission event destruction

Test whether kernel's notification subsystem gets stuck when some fanotify permission events are not responded to. Also test destruction of fanotify instance while there are outstanding permission events. This can result in hanging of processes indefinitely in kernel or in kernel crashes.

Kernel crashes should be fixed by commit 96d41019e3ac "fanotify: fix list corruption in fanotify_get_response()", kernel hangs by "fanotify:
Release SRCU lock when waiting for userspace response" (not yet landed upstream).

Signed-off-by Jan Kara <[email protected]>

---
 runtest/syscalls                                |   1 +
 testcases/kernel/syscalls/fanotify/fanotify07.c | 264 ++++++++++++++++++++++++
 2 files changed, 265 insertions(+)
 create mode 100644 testcases/kernel/syscalls/fanotify/fanotify07.c

OK, I finally got to porting the fanotify permission events test to new LTP api. Here is the result.

runtest/syscalls +1 -0

index 89abac5ff5f8..94232c6cf21e 100644
@@ -473,6 +473,7 @@ fanotify03 fanotify03
 fanotify04 fanotify04
 fanotify05 fanotify05
 fanotify06 fanotify06
+fanotify07 fanotify07
 
 ioperm01 ioperm01
 ioperm02 ioperm02

testcases/kernel/syscalls/fanotify/fanotify07.c new file +0 -0

new file mode 100644
index 000000000000..69722fc365df

testcases/kernel/syscalls/fanotify/fanotify07.c new file +29 -0

+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Further, this software is distributed without any warranty that it is
+ * free of the rightful claim of any third person regarding infringement
+ * or the like.  Any license provided herein, whether implied or
+ * otherwise, applies only to this software file.  Patent licenses, if
+ * any, provided herein do not apply to combinations of this program with
+ * other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Started by Jan Kara <[email protected]>
+ *
+ * DESCRIPTION
+ *     Check that fanotify permission events are handled properly on instance
+ *     destruction.
+ */
+#define _GNU_SOURCE
+#include "config.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>

testcases/kernel/syscalls/fanotify/fanotify07.c new file +51 -0

+#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 children we don't respond to before stopping */
+#define MAX_NOT_RESPONDED 4
+
+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 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);
+			generate_events();
+			exit(0);
+		}
+	}
+}
+
+static int stop_children(void)
+{
+	int child_ret;

testcases/kernel/syscalls/fanotify/fanotify07.c new file +45 -0

+		if (!WIFSIGNALED(child_ret))
+			ret = 1;
+	}
+
+	return ret;
+}
+
+static int setup_instance(void)
+{
+	int fd;
+
+	if ((fd = fanotify_init(FAN_CLASS_CONTENT, O_RDONLY)) < 0) {
+		if (errno == ENOSYS) {
+			tst_brk(TCONF,
+				"fanotify is not configured in this kernel.");
+		} else {
+			tst_brk(TBROK | TERRNO, "fanotify_init failed");
+		}
+	}
+
+	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 loose_fanotify_events(void)
+{
+	int ret;
+	int not_responded = 0;
+
+	/*
+	 * check events
+	 */

testcases/kernel/syscalls/fanotify/fanotify07.c new file +12 -0

+		if (event.mask != FAN_ACCESS_PERM) {
+			tst_res(TFAIL,
+				"get event: mask=%llx (expected %llx) "
+				"pid=%u fd=%u",
+				(unsigned long long)event.mask,
+				(unsigned long long)FAN_ACCESS_PERM,
+				(unsigned)event.pid, event.fd);
+			break;
+		}
+
+		/*
+		 * We respond to permission event with 95% percent

testcases/kernel/syscalls/fanotify/fanotify07.c new file +10 -0

+	}
+}
+
+static void test_fanotify(void)
+{
+	int newfd;
+	int ret;
+
+	fd_notify = setup_instance();
+	run_children();

testcases/kernel/syscalls/fanotify/fanotify07.c new file +7 -0

+	fd_notify = -1;
+
+	ret = stop_children();
+	if (ret)
+		tst_res(TFAIL, "child exited for unexpected reason");
+	else
+		tst_res(TPASS, "all children exited successfully");

testcases/kernel/syscalls/fanotify/fanotify07.c new file +10 -0

+}
+
+static struct tst_test test = {
+	.tid = "fanotify07",
+	.test_all = test_fanotify,
+	.setup = setup,
+	.cleanup = cleanup,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.needs_root = 1,

Hi!

Quoted 6 lines

Test whether kernel's notification subsystem gets stuck when some fanotify permission events are not responded to. Also test destruction of fanotify instance while there are outstanding permission events. This can result in hanging of processes indefinitely in kernel or in kernel crashes.

Quoted 4 lines

Kernel crashes should be fixed by commit 96d41019e3ac "fanotify: fix list corruption in fanotify_get_response()", kernel hangs by "fanotify:
Release SRCU lock when waiting for userspace response" (not yet landed upstream).

Ideally the testcase should include both commit ids in the test description as well. So either we wait until the fix gets into mainline, or add it later.