Add tests to verify sealing memfds with the F_SEAL_AUTO_ALLOCATE works
as expected.

Signed-off-by: Chao Peng <redacted>
---
 tools/testing/selftests/memfd/memfd_test.c | 166 +++++++++++++++++++++
 1 file changed, 166 insertions(+)

diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 94df2692e6e4..b849ece295fd 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c

@@ -9,6 +9,7 @@
 #include <fcntl.h>
 #include <linux/memfd.h>
 #include <sched.h>
+#include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <signal.h>

@@ -232,6 +233,31 @@ static void mfd_fail_open(int fd, int flags, mode_t mode)
 	}
 }
 
+static void mfd_assert_fallocate(int fd)
+{
+	int r;
+
+	r = fallocate(fd, 0, 0, mfd_def_size);
+	if (r < 0) {
+		printf("fallocate(ALLOC) failed: %m\n");
+		abort();
+	}
+}
+
+static void mfd_assert_punch_hole(int fd)
+{
+	int r;
+
+	r = fallocate(fd,
+		      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+		      0,
+		      mfd_def_size);
+	if (r < 0) {
+		printf("fallocate(PUNCH_HOLE) failed: %m\n");
+		abort();
+	}
+}
+
 static void mfd_assert_read(int fd)
 {
 	char buf[16];

@@ -594,6 +620,94 @@ static void mfd_fail_grow_write(int fd)
 	}
 }
 
+static void mfd_assert_hole_write(int fd)
+{
+	ssize_t l;
+	void *p;
+	char *p1;
+
+	/*
+	 * huegtlbfs does not support write, but we want to
+	 * verify everything else here.
+	 */
+	if (!hugetlbfs_test) {
+		/* verify direct write() succeeds */
+		l = write(fd, "\0\0\0\0", 4);
+		if (l != 4) {
+			printf("write() failed: %m\n");
+			abort();
+		}
+	}
+
+	/* verify mmaped write succeeds */
+	p = mmap(NULL,
+		 mfd_def_size,
+		 PROT_READ | PROT_WRITE,
+		 MAP_SHARED,
+		 fd,
+		 0);
+	if (p == MAP_FAILED) {
+		printf("mmap() failed: %m\n");
+		abort();
+	}
+	p1 = (char *)p + mfd_def_size - 1;
+	*p1 = 'H';
+	if (*p1 != 'H') {
+		printf("mmaped write failed: %m\n");
+		abort();
+
+	}
+	munmap(p, mfd_def_size);
+}
+
+sigjmp_buf jbuf, *sigbuf;
+static void sig_handler(int sig, siginfo_t *siginfo, void *ptr)
+{
+	if (sig == SIGBUS) {
+		if (sigbuf)
+			siglongjmp(*sigbuf, 1);
+		abort();
+	}
+}
+
+static void mfd_fail_hole_write(int fd)
+{
+	ssize_t l;
+	void *p;
+	char *p1;
+
+	/* verify direct write() fails */
+	l = write(fd, "data", 4);
+	if (l > 0) {
+		printf("expected failure on write(), but got %d: %m\n", (int)l);
+		abort();
+	}
+
+	/* verify mmaped write fails */
+	p = mmap(NULL,
+		 mfd_def_size,
+		 PROT_READ | PROT_WRITE,
+		 MAP_SHARED,
+		 fd,
+		 0);
+	if (p == MAP_FAILED) {
+		printf("mmap() failed: %m\n");
+		abort();
+	}
+
+	sigbuf = &jbuf;
+	if (sigsetjmp(*sigbuf, 1))
+		goto out;
+
+	/* Below write should trigger SIGBUS signal */
+	p1 = (char *)p + mfd_def_size - 1;
+	*p1 = 'H';

+	printf("failed to receive SIGBUS for mmaped write: %m\n");
+	abort();
+out:
+	munmap(p, mfd_def_size);
+}
+
 static int idle_thread_fn(void *arg)
 {
 	sigset_t set;

@@ -880,6 +994,57 @@ static void test_seal_resize(void)
 	close(fd);
 }
 
+/*
+ * Test F_SEAL_AUTO_ALLOCATE
+ * Test whether F_SEAL_AUTO_ALLOCATE actually prevents allocation.
+ */
+static void test_seal_auto_allocate(void)
+{
+	struct sigaction act;
+	int fd;
+
+	printf("%s SEAL-AUTO-ALLOCATE\n", memfd_str);
+
+	memset(&act, 0, sizeof(act));
+	act.sa_sigaction = sig_handler;
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGBUS, &act, 0)) {
+		printf("sigaction() failed: %m\n");
+		abort();
+	}
+
+	fd = mfd_assert_new("kern_memfd_seal_auto_allocate",
+			    mfd_def_size,
+			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+	/* read/write should pass if F_SEAL_AUTO_ALLOCATE not set */
+	mfd_assert_read(fd);
+	mfd_assert_hole_write(fd);
+
+	mfd_assert_has_seals(fd, 0);
+	mfd_assert_add_seals(fd, F_SEAL_AUTO_ALLOCATE);
+	mfd_assert_has_seals(fd, F_SEAL_AUTO_ALLOCATE);
+
+	/* read/write should pass for pre-allocated area */
+	mfd_assert_read(fd);
+	mfd_assert_hole_write(fd);
+
+	mfd_assert_punch_hole(fd);
+
+	/* read should pass, write should fail in hole */
+	mfd_assert_read(fd);
+	mfd_fail_hole_write(fd);
+
+	mfd_assert_fallocate(fd);
+
+	/* read/write should pass after fallocate */
+	mfd_assert_read(fd);
+	mfd_assert_hole_write(fd);
+
+	close(fd);
+}