generic: test that truncate(2) on fsverity is blocked

truncate(2) doesn't go through open and needs special code to block
it on fsverity files.  btrfs was missing this check.

Note that truncate(2) in current core utils uses openat and ftruncate,
so add our own little test program for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/.gitignore b/.gitignore
index 82c57f4153013052b6b62e9c6f8322ee9adbb981..2b5bedd59fceb886e344116d8d8e67ed10dcefb6 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -212,6 +212,7 @@ tags
 /src/dio-writeback-race
 /src/unlink-fsync
 /src/file_attr
+/src/truncate
 
 # Symlinked files
 /tests/generic/035.out

diff --git a/src/Makefile b/src/Makefile
index d0a4106e6be81b61a3ef75efa8825569f780a693..577d816ae859b67b510994b503a58f828750f36d 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -21,7 +21,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
        t_mmap_writev_overlap checkpoint_journal mmap-rw-fault allocstale \
        t_mmap_cow_memory_failure fake-dump-rootino dio-buf-fault rewinddir-test \
        readdir-while-renames dio-append-buf-fault dio-write-fsync-same-fd \
-       dio-writeback-race unlink-fsync
+       dio-writeback-race unlink-fsync truncate
 
 LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
        preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \

diff --git a/src/truncate.c b/src/truncate.c
new file mode 100644 (file)
index 0000000..4c106d2
--- /dev/null
+++ b/src/truncate.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2026 Christoph Hellwig.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+       if (truncate(argv[1], 0) < 0) {
+               perror("truncate");
+               exit(1);
+       }
+
+       fprintf(stderr, "truncate succeeded\n");
+}

diff --git a/tests/generic/788 b/tests/generic/788
new file mode 100755 (executable)
index 0000000..ac4720d
--- /dev/null
+++ b/tests/generic/788
@@ -0,0 +1,38 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Christoph Hellwig.
+#
+# FS QA Test 788
+#
+# Test that truncate(2) is blocked on fsverity files.
+#
+. ./common/preamble
+_begin_fstest auto quick verity
+
+_cleanup()
+{
+       cd /
+       _restore_fsverity_signatures
+       rm -f $tmp.*
+}
+
+. ./common/filter
+. ./common/verity
+
+_require_scratch_verity
+_require_test_program "truncate"
+
+_disable_fsverity_signatures
+
+_scratch_mkfs_verity &>> $seqres.full
+_scratch_mount
+
+fsv_file=$SCRATCH_MNT/file.fsv
+
+_fsv_scratch_begin_subtest "Using truncate(2) on a verity file fails"
+_fsv_create_enable_file $fsv_file
+$here/src/truncate $fsv_file
+
+# success, all done
+status=0
+exit

diff --git a/tests/generic/788.out b/tests/generic/788.out
new file mode 100644 (file)
index 0000000..11074b7
--- /dev/null
+++ b/tests/generic/788.out
@@ -0,0 +1,4 @@
+QA output created by 788
+
+# Using truncate(2) on a verity file fails
+truncate: Operation not permitted