+ selftests-liveupdate-add-test-for-double-preservation.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests: liveupdate: add test for double preservation
has been added to the -mm mm-new branch.  Its filename is
     selftests-liveupdate-add-test-for-double-preservation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-liveupdate-add-test-for-double-preservation.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: selftests: liveupdate: add test for double preservation
Date: Thu, 26 Mar 2026 16:39:43 +0000

Verify that a file can only be preserved once across all active sessions. 
Attempting to preserve it a second time, whether in the same or a
different session, should fail with EBUSY.

Link: https://lkml.kernel.org/r/20260326163943.574070-4-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/liveupdate/liveupdate.c |   41 ++++++++++++++
 1 file changed, 41 insertions(+)

--- a/tools/testing/selftests/liveupdate/liveupdate.c~selftests-liveupdate-add-test-for-double-preservation
+++ a/tools/testing/selftests/liveupdate/liveupdate.c
@@ -345,4 +345,45 @@ TEST_F(liveupdate_device, preserve_unsup
 	ASSERT_EQ(close(session_fd), 0);
 }
 
+/*
+ * Test Case: Prevent Double Preservation
+ *
+ * Verifies that a file (memfd) can only be preserved once across all active
+ * sessions. Attempting to preserve it a second time, whether in the same or
+ * a different session, should fail with EBUSY.
+ */
+TEST_F(liveupdate_device, prevent_double_preservation)
+{
+	int session_fd1, session_fd2, mem_fd;
+	int ret;
+
+	self->fd1 = open(LIVEUPDATE_DEV, O_RDWR);
+	if (self->fd1 < 0 && errno == ENOENT)
+		SKIP(return, "%s does not exist", LIVEUPDATE_DEV);
+	ASSERT_GE(self->fd1, 0);
+
+	session_fd1 = create_session(self->fd1, "double-preserve-session-1");
+	ASSERT_GE(session_fd1, 0);
+	session_fd2 = create_session(self->fd1, "double-preserve-session-2");
+	ASSERT_GE(session_fd2, 0);
+
+	mem_fd = memfd_create("test-memfd", 0);
+	ASSERT_GE(mem_fd, 0);
+
+	/* First preservation should succeed */
+	ASSERT_EQ(preserve_fd(session_fd1, mem_fd, 0x1111), 0);
+
+	/* Second preservation in a different session should fail with EBUSY */
+	ret = preserve_fd(session_fd2, mem_fd, 0x2222);
+	EXPECT_EQ(ret, -EBUSY);
+
+	/* Second preservation in the same session (different token) should fail with EBUSY */
+	ret = preserve_fd(session_fd1, mem_fd, 0x3333);
+	EXPECT_EQ(ret, -EBUSY);
+
+	ASSERT_EQ(close(mem_fd), 0);
+	ASSERT_EQ(close(session_fd1), 0);
+	ASSERT_EQ(close(session_fd2), 0);
+}
+
 TEST_HARNESS_MAIN
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

liveupdate-protect-file-handler-list-with-rwsem.patch
liveupdate-protect-flb-lists-with-rwsem.patch
liveupdate-remove-file-handler-module-refcounting.patch
liveupdate-defer-flb-module-refcounting-to-active-sessions.patch
liveupdate-remove-luo_session_quiesce.patch
liveupdate-auto-unregister-flbs-on-file-handler-unregistration.patch
liveupdate-remove-liveupdate_test_unregister.patch
liveupdate-make-unregister-functions-return-void.patch
liveupdate-prevent-double-management-of-files.patch
memfd-implement-get_id-for-memfd_luo.patch
selftests-liveupdate-add-test-for-double-preservation.patch