chmod02.c: Block mode changes of symlinks

Signed-off-by: Wei Gao <wegao@suse.com>

runtest/syscalls

@@ -68,6 +68,7 @@ chdir04 chdir04
 
 chmod01 chmod01
 chmod01A symlink01 -T chmod01
+chmod02 chmod02
 chmod03 chmod03
 chmod05 chmod05
 chmod06 chmod06

testcases/kernel/syscalls/chmod/.gitignore

@@ -1,4 +1,5 @@
 /chmod01
+/chmod02
 /chmod03
 /chmod05
 /chmod06

testcases/kernel/syscalls/chmod/chmod02.c

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2024 Wei Gao <wegao@suse.com>
+ */
+
+/*\
+ * [Description]
+ *
+ * Test for kernel commit 5d1f903f75a80daa4dfb3d84e114ec8ecbf29956
+ * "attr: block mode changes of symlinks".
+ *
+ */
+
+#include "lapi/fcntl.h"
+#include "tst_test.h"
+
+#define MODE 0644
+#define TESTFILE "testfile"
+#define TESTFILE_SYMLINK "testfile_symlink"
+#define MNTPOINT "mntpoint"
+
+static void run(void)
+{
+	struct stat stat_file, stat_sym;
+	int mode = 0;
+	char fd_path[100];
+
+	int fd = SAFE_OPEN(TESTFILE_SYMLINK, O_PATH | O_NOFOLLOW);
+
+	sprintf(fd_path, "/proc/self/fd/%d", fd);
+
+	TST_EXP_FAIL(chmod(fd_path, mode), ENOTSUP, "chmod(%s, %04o)",
+			TESTFILE_SYMLINK, mode);
+
+	SAFE_STAT(TESTFILE, &stat_file);
+	SAFE_LSTAT(TESTFILE_SYMLINK, &stat_sym);
+
+	stat_file.st_mode &= ~S_IFREG;
+	stat_sym.st_mode &= ~S_IFLNK;
+
+	if (stat_file.st_mode == (unsigned int)mode) {
+		tst_res(TFAIL, "stat(%s) mode=%04o",
+				TESTFILE, stat_file.st_mode);
+	} else {
+		tst_res(TPASS, "stat(%s) mode=%04o",
+				TESTFILE, stat_file.st_mode);
+	}
+
+	if (stat_sym.st_mode == (unsigned int)mode) {
+		tst_res(TFAIL, "stat(%s) mode=%04o",
+				TESTFILE_SYMLINK, stat_sym.st_mode);
+	} else {
+		tst_res(TPASS, "stat(%s) mode=%04o",
+				TESTFILE_SYMLINK, stat_sym.st_mode);
+	}
+
+	SAFE_CLOSE(fd);
+}
+
+static void setup(void)
+{
+	SAFE_CHDIR(MNT_POINT);
+	SAFE_TOUCH(TESTFILE, MODE, NULL);
+	SAFE_SYMLINK(TESTFILE, TESTFILE_SYMLINK);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.test_all = run,
+	.needs_tmpdir = 1,
+	.min_kver = "6.6",
+	.mount_device = 1,
+	.mntpoint = MNTPOINT,
+	.all_filesystems = 1
+};