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// SPDX-License-Identifier: GPL-2.0
/*
* F_SET_RW_HINT is refused on an immutable inode. Nothing is ever written
* to it and it may be shared with everybody, like a namespace file or the
* root of an empty mount namespace.
*/
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include "../kselftest_harness.h"
/* <linux/fs.h> and <linux/fcntl.h> don't mix with the libc headers */
#ifndef FS_IOC_GETFLAGS
#define FS_IOC_GETFLAGS _IOR('f', 1, long)
#define FS_IOC_SETFLAGS _IOW('f', 2, long)
#endif
#ifndef FS_IMMUTABLE_FL
#define FS_IMMUTABLE_FL 0x00000010
#endif
#ifndef F_LINUX_SPECIFIC_BASE
#define F_LINUX_SPECIFIC_BASE 1024
#endif
#ifndef F_GET_RW_HINT
#define F_GET_RW_HINT (F_LINUX_SPECIFIC_BASE + 11)
#define F_SET_RW_HINT (F_LINUX_SPECIFIC_BASE + 12)
#endif
#ifndef RWH_WRITE_LIFE_SHORT
#define RWH_WRITE_LIFE_SHORT 2
#endif
#ifndef UNSHARE_EMPTY_MNTNS
#define UNSHARE_EMPTY_MNTNS 0x00100000
#endif
static int set_hint(int fd, uint64_t hint)
{
return fcntl(fd, F_SET_RW_HINT, &hint);
}
static long get_hint(int fd)
{
uint64_t hint;
if (fcntl(fd, F_GET_RW_HINT, &hint))
return -1;
return hint;
}
TEST(immutable_file)
{
char path[] = "/tmp/rw_hint.XXXXXX";
int fd, flags;
if (geteuid())
SKIP(return, "test requires root");
fd = mkstemp(path);
ASSERT_GE(fd, 0);
unlink(path);
ASSERT_EQ(set_hint(fd, RWH_WRITE_LIFE_SHORT), 0);
EXPECT_EQ(get_hint(fd), RWH_WRITE_LIFE_SHORT);
if (ioctl(fd, FS_IOC_GETFLAGS, &flags)) {
close(fd);
SKIP(return, "no file attributes on this filesystem");
}
flags |= FS_IMMUTABLE_FL;
ASSERT_EQ(ioctl(fd, FS_IOC_SETFLAGS, &flags), 0);
EXPECT_EQ(set_hint(fd, RWH_WRITE_LIFE_SHORT), -1);
EXPECT_EQ(errno, EPERM);
flags &= ~FS_IMMUTABLE_FL;
ASSERT_EQ(ioctl(fd, FS_IOC_SETFLAGS, &flags), 0);
EXPECT_EQ(set_hint(fd, RWH_WRITE_LIFE_SHORT), 0);
close(fd);
}
TEST(namespace_file)
{
int fd;
if (geteuid())
SKIP(return, "test requires root");
fd = open("/proc/self/ns/mnt", O_RDONLY | O_CLOEXEC);
ASSERT_GE(fd, 0);
EXPECT_EQ(set_hint(fd, RWH_WRITE_LIFE_SHORT), -1);
EXPECT_EQ(errno, EPERM);
close(fd);
}
TEST(empty_mntns_root)
{
int status;
pid_t pid;
if (geteuid())
SKIP(return, "test requires root");
pid = fork();
ASSERT_GE(pid, 0);
if (pid == 0) {
int fd;
if (unshare(UNSHARE_EMPTY_MNTNS))
_exit(errno == EINVAL ? 100 : 1);
fd = open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC);
if (fd < 0)
_exit(2);
if (set_hint(fd, RWH_WRITE_LIFE_SHORT) == 0)
_exit(3);
_exit(errno == EPERM ? 0 : 4);
}
ASSERT_EQ(waitpid(pid, &status, 0), pid);
ASSERT_TRUE(WIFEXITED(status));
if (WEXITSTATUS(status) == 100)
SKIP(return, "UNSHARE_EMPTY_MNTNS not supported");
EXPECT_EQ(WEXITSTATUS(status), 0);
}
TEST_HARNESS_MAIN
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