[LTP] [PATCH 3/3] fanotify24: add mmap() and user page fault to test

[Amir Goldstein]

Commit 066e053fe208a ("fsnotify: add pre-content hooks on mmap()")
in 6.14-rc7 added a pre-content hooh in mmap() before the final release
of the fsnotify pre-content event feature.

To test pre-content hook on mmap(), increase the size of the test file
to 101 pages use mmap() to setup a buffer from the end of the test file.

Change some of the test cases to allow the write() and use this buffer
as the input buffer to write(), which tests deadlock avoidance by
suppresing pre-content hook on user page faults.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 .../kernel/syscalls/fanotify/fanotify24.c     | 41 ++++++++++++++++---
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/testcases/kernel/syscalls/fanotify/fanotify24.c b/testcases/kernel/syscalls/fanotify/fanotify24.c
index 2d2479b39..3a76f2c1b 100644
--- a/testcases/kernel/syscalls/fanotify/fanotify24.c
+++ b/testcases/kernel/syscalls/fanotify/fanotify24.c
@@ -46,6 +46,7 @@
 static char fname[BUF_SIZE];
 static char buf[BUF_SIZE];
 static volatile int fd_notify;
+static size_t page_sz;
 
 static pid_t child_pid;
 
@@ -68,7 +69,8 @@ static struct tcase {
 		FAN_OPEN_PERM | FAN_PRE_ACCESS,
 		{
 			{FAN_OPEN_PERM, FAN_ALLOW},
-			{FAN_PRE_ACCESS, FAN_DENY},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_PERM, FAN_DENY_ERRNO(EBUSY)}
 		}
@@ -78,6 +80,7 @@ static struct tcase {
 		INIT_FANOTIFY_MARK_TYPE(INODE),
 		FAN_PRE_ACCESS | FAN_OPEN_EXEC_PERM,
 		{
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_EXEC_PERM, FAN_DENY_ERRNO(EBUSY)}
@@ -89,7 +92,8 @@ static struct tcase {
 		FAN_OPEN_PERM | FAN_PRE_ACCESS,
 		{
 			{FAN_OPEN_PERM, FAN_ALLOW},
-			{FAN_PRE_ACCESS, FAN_DENY},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_PERM, FAN_DENY_ERRNO(EBUSY)}
 		}
@@ -99,6 +103,7 @@ static struct tcase {
 		INIT_FANOTIFY_MARK_TYPE(MOUNT),
 		FAN_PRE_ACCESS | FAN_OPEN_EXEC_PERM,
 		{
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_EXEC_PERM, FAN_DENY_ERRNO(EBUSY)}
@@ -110,7 +115,8 @@ static struct tcase {
 		FAN_OPEN_PERM | FAN_PRE_ACCESS,
 		{
 			{FAN_OPEN_PERM, FAN_ALLOW},
-			{FAN_PRE_ACCESS, FAN_DENY},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_PERM, FAN_DENY_ERRNO(EBUSY)}
 		}
@@ -120,6 +126,7 @@ static struct tcase {
 		INIT_FANOTIFY_MARK_TYPE(FILESYSTEM),
 		FAN_PRE_ACCESS | FAN_OPEN_EXEC_PERM,
 		{
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY},
 			{FAN_PRE_ACCESS, FAN_DENY_ERRNO(EIO)},
 			{FAN_OPEN_EXEC_PERM, FAN_DENY_ERRNO(EBUSY)}
@@ -130,6 +137,7 @@ static struct tcase {
 		INIT_FANOTIFY_MARK_TYPE(PARENT),
 		FAN_PRE_ACCESS | FAN_OPEN_EXEC_PERM | FAN_EVENT_ON_CHILD,
 		{
+			{FAN_PRE_ACCESS, FAN_ALLOW},
 			{FAN_PRE_ACCESS, FAN_DENY},
 			{FAN_PRE_ACCESS, FAN_DENY},
 			{FAN_OPEN_EXEC_PERM, FAN_DENY}
@@ -169,6 +177,7 @@ static int expected_errno(unsigned int response)
 static void generate_events(struct tcase *tc)
 {
 	int fd;
+	char *addr;
 	char *const argv[] = {FILE_EXEC_PATH, NULL};
 	struct event *event = tc->event_set;
 	int exp_ret, exp_errno = 0;
@@ -186,8 +195,25 @@ static void generate_events(struct tcase *tc)
 
 	exp_ret = exp_errno ? -1 : 1;
 	errno = 0;
-	/* FAN_PRE_ACCESS events are reported also on write */
-	if (write(fd, fname, 1) != exp_ret || errno != exp_errno) {
+	/*
+	 * FAN_PRE_ACCESS events are reported on map() and write(), but should
+	 * not be reported when faulting in the user page at offset page_sz*100
+	 * that is used as an input buffer to the write() syscall.
+	 */
+	addr = SAFE_MMAP(NULL, page_sz, PROT_READ, MAP_PRIVATE, fd, page_sz*100);
+	if (!addr || errno != exp_errno) {
+		tst_res(TFAIL, "mmap() got errno %d (expected %d)", errno, exp_errno);
+		exit(3);
+	} else if (errno == exp_errno) {
+		tst_res(TINFO, "mmap() got errno %d as expected", errno);
+	}
+
+	exp_errno = expected_errno(event->response);
+	event++;
+
+	exp_ret = exp_errno ? -1 : 1;
+	errno = 0;
+	if (write(fd, addr, 1) != exp_ret || errno != exp_errno) {
 		tst_res(TFAIL, "write() got errno %d (expected %d)", errno, exp_errno);
 		exit(3);
 	} else if (errno == exp_errno) {
@@ -199,7 +225,7 @@ static void generate_events(struct tcase *tc)
 	exp_errno = expected_errno(event->response);
 	event++;
 
-	exp_ret = exp_errno ? -1 : 1;
+	exp_ret = exp_errno ? -1 : BUF_SIZE;
 	errno = 0;
 	if (read(fd, buf, BUF_SIZE) != exp_ret || errno != exp_errno) {
 		tst_res(TFAIL, "read() got errno %d (expected %d)", errno, exp_errno);
@@ -449,8 +475,11 @@ static void test_fanotify(unsigned int n)
 
 static void setup(void)
 {
+	page_sz = getpagesize();
+
 	sprintf(fname, MOUNT_PATH"/fname_%d", getpid());
 	SAFE_FILE_PRINTF(fname, "1");
+	SAFE_TRUNCATE(fname, page_sz*101);
 
 	REQUIRE_FANOTIFY_EVENTS_SUPPORTED_ON_FS(FAN_CLASS_PRE_CONTENT, FAN_MARK_FILESYSTEM,
 						FAN_PRE_ACCESS, fname);
-- 
2.34.1