[LTP] [PATCH v2] Add ioctl_loop08 test for LOOP_GET_STATUS lock imbalance

[xiaoshoukui <xiaoshoukui@gmail.com>]

---
 .../kernel/syscalls/ioctl/ioctl_loop08.c      | 147 ++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 testcases/kernel/syscalls/ioctl/ioctl_loop08.c

diff --git a/testcases/kernel/syscalls/ioctl/ioctl_loop08.c b/testcases/kernel/syscalls/ioctl/ioctl_loop08.c
new file mode 100644
index 000000000..047273576
--- /dev/null
+++ b/testcases/kernel/syscalls/ioctl/ioctl_loop08.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2022 xiaoshoukui <xiaoshoukui@ruijie.com.cn>
+ */
+
+/*\
+ * [Description]
+ *
+ * This is a basic ioctl test about loopdevice LOOP_GET_STATUS
+ * and LOOP_GET_STATUS64.
+ * Commit 2d1d4c1e591f made loop_get_status() drop lo_ctx_mutex before
+ * returning, but the loop_get_status_old(), loop_get_status64(), and
+ * loop_get_status_compat() wrappers don't call loop_get_status() if the
+ * passed argument is NULL. The callers expect that the lock is dropped, so
+ * make sure we drop it in that case, too.
+ *
+ * Fixed by commit:
+ *
+ *  commit bdac616db9bbadb90b7d6a406144571015e138f7
+ *  Author: Omar Sandoval <osandov@fb.com>
+ *  Date:   Fri Apr 06 09:57:03 2018 -0700
+ *
+ *    loop: fix LOOP_GET_STATUS lock imbalance
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <stdlib.h>
+#include "lapi/loop.h"
+#include "tst_test.h"
+
+#define MAX_MSGSIZE 4096
+
+static const char lock_imbalance[] = "lock held when returning to user space";
+
+static struct tcase {
+	int ioctl_flag;
+	char *message;
+} tcases[] = {
+	{ LOOP_GET_STATUS,
+	 "Testing LOOP_GET_STATUS lock imbalance" },
+
+	{ LOOP_GET_STATUS64,
+	 "Testing LOOP_GET_STATUS64 lock imbalance" },
+};
+
+static int find_kmsg(const char *text_to_find)
+{
+	int f, msg_found = 0;
+	char msg[MAX_MSGSIZE + 1];
+
+	f = SAFE_OPEN("/dev/kmsg", O_RDONLY | O_NONBLOCK);
+
+	while (1) {
+		TEST(read(f, msg, MAX_MSGSIZE));
+		if (TST_RET < 0) {
+			if (TST_ERR == EAGAIN)
+				/* there are no more messages */
+				break;
+			else if (TST_ERR == EPIPE)
+				/* current message was overwritten */
+				continue;
+			else
+				tst_brk(TBROK | TTERRNO,
+					"err reading /dev/kmsg");
+		} else {
+			/* lines from kmsg are not NULL terminated */
+			msg[TST_RET] = '\0';
+			if (strstr(msg, text_to_find) != NULL) {
+				msg_found = 1;
+				break;
+			}
+		}
+	}
+	SAFE_CLOSE(f);
+
+	if (msg_found)
+		return 0;
+	else
+		return -1;
+}
+
+static void do_child(void)
+{
+	char dev_path[1024];
+	int dev_num, dev_fd;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(tcases); i++) {
+		tst_res(TINFO, "%s", tcases[i].message);
+		dev_num = tst_find_free_loopdev(dev_path, sizeof(dev_path));
+
+		if (dev_num < 0)
+			tst_brk(TBROK, "Failed to find free loop device");
+
+		dev_fd = SAFE_OPEN(dev_path, O_RDWR);
+
+		if (tcases[i].ioctl_flag == LOOP_GET_STATUS)
+			ioctl(dev_fd, LOOP_GET_STATUS, NULL);
+		else
+			ioctl(dev_fd, LOOP_GET_STATUS64, NULL);
+
+		if (dev_fd > 0)
+			SAFE_CLOSE(dev_fd);
+
+	}
+
+	exit(0);
+
+}
+
+static void verify_ioctl_loop(void)
+{
+	int ret, pid;
+
+	pid = SAFE_FORK();
+	if (!pid)
+		do_child();
+
+	ret = TST_PROCESS_STATE_WAIT(pid, 'D', 5000);
+
+	if (!ret && !find_kmsg(lock_imbalance))
+		tst_res(TFAIL, "Trigger ioctl loop lock imbalance");
+	else
+		tst_res(TPASS, "Nothing bad happened, probably");
+
+}
+
+static struct tst_test test = {
+	.test_all = verify_ioctl_loop,
+	.needs_root = 1,
+	.needs_kconfigs = (const char *[]) {
+		"CONFIG_LOCKDEP=y",
+		NULL
+	},
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "bdac616db9bb "},
+		{}
+	},
+	.needs_drivers = (const char *const[]) {
+		"loop",
+		NULL
+	},
+	.forks_child = 1,
+	.timeout = 60,
+};
-- 
2.20.1


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