[PATCH] generic: add a testcase to check the capability CAP_LINUX_IMMUTABLE

[Jiufei Xue <jiufei.xue@linux.alibaba.com>]

It should return error while changing IMMUTABLE_FL and APPEND_FL if the
process has no capability CAP_LINUX_IMMUTABLE.

However, it's not true on overlayfs after kernel version v4.19 since
the process's subjective cred is overridden with ofs->creator_cred
before calling real vfs_ioctl.

The following patch for ovl fix the problem:
  "ovl: check the capability before cred overridden"

Add this testcase to cover this bug.

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
---
v2: add testcases for APPEND_FL and flags clearing. Suggested by
    Amir Goldstein.
v3: clear the flags on both the file in cleanup() in case test is
    aborted.

 common/config         |  1 +
 tests/generic/545     | 73 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/545.out | 10 ++++++
 tests/generic/group   |  1 +
 4 files changed, 85 insertions(+)
 create mode 100755 tests/generic/545
 create mode 100755 tests/generic/545.out

diff --git a/common/config b/common/config
index 64f87057..364432bb 100644
--- a/common/config
+++ b/common/config
@@ -196,6 +196,7 @@ export SQLITE3_PROG="$(type -P sqlite3)"
 export TIMEOUT_PROG="$(type -P timeout)"
 export SETCAP_PROG="$(type -P setcap)"
 export GETCAP_PROG="$(type -P getcap)"
+export CAPSH_PROG="$(type -P capsh)"
 export CHECKBASHISMS_PROG="$(type -P checkbashisms)"
 export XFS_INFO_PROG="$(type -P xfs_info)"
 export DUPEREMOVE_PROG="$(type -P duperemove)"
diff --git a/tests/generic/545 b/tests/generic/545
new file mode 100755
index 00000000..da2eac2e
--- /dev/null
+++ b/tests/generic/545
@@ -0,0 +1,73 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2019 Alibaba Group.  All Rights Reserved.
+#
+# FS QA Test No. 545
+#
+# Check that we can't set the FS_APPEND_FL and FS_IMMUTABLE_FL inode
+# flags without capbility CAP_LINUX_IMMUTABLE
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1    # failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+    # Cleanup of flags on both file in case test is aborted
+    # (i.e. CTRL-C), so we have no immutable/append-only files
+    $CHATTR_PROG -ia $testdir/file1 2>&1
+    $CHATTR_PROG -ia $testdir/file2 2>&1
+
+    cd /
+    rm -rf $tmp.* $testdir
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/attr
+
+# real QA test starts here
+_supported_os Linux
+_require_chattr i
+_require_chattr a
+_require_command "$CAPSH_PROG" "capsh"
+
+echo "Format and mount"
+testdir="$TEST_DIR/test-$seq"
+rm -rf $testdir
+mkdir $testdir
+
+echo "Create the original files"
+touch $testdir/file1
+touch $testdir/file2
+
+do_filter_output()
+{
+    err_str=`_filter_test_dir | grep "Operation not permitted"`
+    test -n "$err_str" && echo "Operation not permitted"
+}
+
+echo "Try to chattr +ia with capabilities CAP_LINUX_IMMUTABLE"
+$CHATTR_PROG +a $testdir/file1 2>&1
+$CHATTR_PROG +i $testdir/file1 2>&1
+
+echo "Try to chattr +ia/-ia without capability CAP_LINUX_IMMUTABLE"
+$CAPSH_PROG --drop=cap_linux_immutable -- -c "$CHATTR_PROG +a $testdir/file2" 2>&1 | do_filter_output
+$CAPSH_PROG --drop=cap_linux_immutable -- -c "$CHATTR_PROG +i $testdir/file2" 2>&1 | do_filter_output
+
+$CAPSH_PROG --drop=cap_linux_immutable -- -c "$CHATTR_PROG -i $testdir/file1" 2>&1 | do_filter_output
+$CAPSH_PROG --drop=cap_linux_immutable -- -c "$CHATTR_PROG -a $testdir/file1" 2>&1 | do_filter_output
+
+echo "Try to chattr -ia with capability CAP_LINUX_IMMUTABLE"
+$CHATTR_PROG -i $testdir/file1 2>&1
+$CHATTR_PROG -a $testdir/file1 2>&1
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/545.out b/tests/generic/545.out
new file mode 100755
index 00000000..8c6e4082
--- /dev/null
+++ b/tests/generic/545.out
@@ -0,0 +1,10 @@
+QA output created by 545
+Format and mount
+Create the original files
+Try to chattr +ia with capabilities CAP_LINUX_IMMUTABLE
+Try to chattr +ia/-ia without capability CAP_LINUX_IMMUTABLE
+Operation not permitted
+Operation not permitted
+Operation not permitted
+Operation not permitted
+Try to chattr -ia with capability CAP_LINUX_IMMUTABLE
diff --git a/tests/generic/group b/tests/generic/group
index 40deb4d0..7a457e81 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -547,3 +547,4 @@
 542 auto quick clone
 543 auto quick clone
 544 auto quick clone
+545 auto quick cap
-- 
2.19.1.856.g8858448bb