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Systemd/src/basic/stat-util.c
Zbigniew Jędrzejewski-Szmek a5648b8094 basic/fs-util: change CHASE_OPEN flag into a separate output parameter 
chase_symlinks() would return negative on error, and either a non-negative status
or a non-negative fd when CHASE_OPEN was given. This made the interface quite
complicated, because dependning on the flags used, we would get two different
"types" of return object. Coverity was always confused by this, and flagged
every use of chase_symlinks() without CHASE_OPEN as a resource leak (because it
would this that an fd is returned). This patch uses a saparate output parameter,
so there is no confusion.

(I think it is OK to have functions which return either an error or an fd. It's
only returning *either* an fd or a non-fd that is confusing.)
2019-10-24 22:44:24 +09:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/magic.h>
#include <sched.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "fs-util.h"
#include "macro.h"
#include "missing.h"
#include "parse-util.h"
#include "stat-util.h"
#include "string-util.h"
int is_symlink(const char *path) {
struct stat info;
assert(path);
if (lstat(path, &info) < 0)
return -errno;
return !!S_ISLNK(info.st_mode);
}
int is_dir(const char* path, bool follow) {
struct stat st;
int r;
assert(path);
if (follow)
r = stat(path, &st);
else
r = lstat(path, &st);
if (r < 0)
return -errno;
return !!S_ISDIR(st.st_mode);
}
int is_dir_fd(int fd) {
struct stat st;
if (fstat(fd, &st) < 0)
return -errno;
return !!S_ISDIR(st.st_mode);
}
int is_device_node(const char *path) {
struct stat info;
assert(path);
if (lstat(path, &info) < 0)
return -errno;
return !!(S_ISBLK(info.st_mode) || S_ISCHR(info.st_mode));
}
int dir_is_empty_at(int dir_fd, const char *path) {
_cleanup_close_ int fd = -1;
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
if (path)
fd = openat(dir_fd, path, O_RDONLY|O_DIRECTORY|O_CLOEXEC);
else
fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
if (fd < 0)
return -errno;
d = fdopendir(fd);
if (!d)
return -errno;
fd = -1;
FOREACH_DIRENT(de, d, return -errno)
return 0;
return 1;
}
bool null_or_empty(struct stat *st) {
assert(st);
if (S_ISREG(st->st_mode) && st->st_size <= 0)
return true;
/* We don't want to hardcode the major/minor of /dev/null,
* hence we do a simpler "is this a device node?" check. */
if (S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
return true;
return false;
}
int null_or_empty_path(const char *fn) {
struct stat st;
assert(fn);
if (stat(fn, &st) < 0)
return -errno;
return null_or_empty(&st);
}
int null_or_empty_fd(int fd) {
struct stat st;
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
return null_or_empty(&st);
}
int path_is_read_only_fs(const char *path) {
struct statvfs st;
assert(path);
if (statvfs(path, &st) < 0)
return -errno;
if (st.f_flag & ST_RDONLY)
return true;
/* On NFS, statvfs() might not reflect whether we can actually
* write to the remote share. Let's try again with
* access(W_OK) which is more reliable, at least sometimes. */
if (access(path, W_OK) < 0 && errno == EROFS)
return true;
return false;
}
int files_same(const char *filea, const char *fileb, int flags) {
struct stat a, b;
assert(filea);
assert(fileb);
if (fstatat(AT_FDCWD, filea, &a, flags) < 0)
return -errno;
if (fstatat(AT_FDCWD, fileb, &b, flags) < 0)
return -errno;
return a.st_dev == b.st_dev &&
a.st_ino == b.st_ino;
}
bool is_fs_type(const struct statfs *s, statfs_f_type_t magic_value) {
assert(s);
assert_cc(sizeof(statfs_f_type_t) >= sizeof(s->f_type));
return F_TYPE_EQUAL(s->f_type, magic_value);
}
int fd_is_fs_type(int fd, statfs_f_type_t magic_value) {
struct statfs s;
if (fstatfs(fd, &s) < 0)
return -errno;
return is_fs_type(&s, magic_value);
}
int path_is_fs_type(const char *path, statfs_f_type_t magic_value) {
_cleanup_close_ int fd = -1;
fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
if (fd < 0)
return -errno;
return fd_is_fs_type(fd, magic_value);
}
bool is_temporary_fs(const struct statfs *s) {
return is_fs_type(s, TMPFS_MAGIC) ||
is_fs_type(s, RAMFS_MAGIC);
}
bool is_network_fs(const struct statfs *s) {
return is_fs_type(s, CIFS_MAGIC_NUMBER) ||
is_fs_type(s, CODA_SUPER_MAGIC) ||
is_fs_type(s, NCP_SUPER_MAGIC) ||
is_fs_type(s, NFS_SUPER_MAGIC) ||
is_fs_type(s, SMB_SUPER_MAGIC) ||
is_fs_type(s, V9FS_MAGIC) ||
is_fs_type(s, AFS_SUPER_MAGIC) ||
is_fs_type(s, OCFS2_SUPER_MAGIC);
}
int fd_is_temporary_fs(int fd) {
struct statfs s;
if (fstatfs(fd, &s) < 0)
return -errno;
return is_temporary_fs(&s);
}
int fd_is_network_fs(int fd) {
struct statfs s;
if (fstatfs(fd, &s) < 0)
return -errno;
return is_network_fs(&s);
}
int path_is_temporary_fs(const char *path) {
_cleanup_close_ int fd = -1;
fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
if (fd < 0)
return -errno;
return fd_is_temporary_fs(fd);
}
int stat_verify_regular(const struct stat *st) {
assert(st);
/* Checks whether the specified stat() structure refers to a regular file. If not returns an appropriate error
* code. */
if (S_ISDIR(st->st_mode))
return -EISDIR;
if (S_ISLNK(st->st_mode))
return -ELOOP;
if (!S_ISREG(st->st_mode))
return -EBADFD;
return 0;
}
int fd_verify_regular(int fd) {
struct stat st;
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
return stat_verify_regular(&st);
}
int stat_verify_directory(const struct stat *st) {
assert(st);
if (S_ISLNK(st->st_mode))
return -ELOOP;
if (!S_ISDIR(st->st_mode))
return -ENOTDIR;
return 0;
}
int fd_verify_directory(int fd) {
struct stat st;
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
return stat_verify_directory(&st);
}
int device_path_make_major_minor(mode_t mode, dev_t devno, char **ret) {
const char *t;
/* Generates the /dev/{char|block}/MAJOR:MINOR path for a dev_t */
if (S_ISCHR(mode))
t = "char";
else if (S_ISBLK(mode))
t = "block";
else
return -ENODEV;
if (asprintf(ret, "/dev/%s/%u:%u", t, major(devno), minor(devno)) < 0)
return -ENOMEM;
return 0;
}
int device_path_make_canonical(mode_t mode, dev_t devno, char **ret) {
_cleanup_free_ char *p = NULL;
int r;
/* Finds the canonical path for a device, i.e. resolves the /dev/{char|block}/MAJOR:MINOR path to the end. */
assert(ret);
if (major(devno) == 0 && minor(devno) == 0) {
char *s;
/* A special hack to make sure our 'inaccessible' device nodes work. They won't have symlinks in
* /dev/block/ and /dev/char/, hence we handle them specially here. */
if (S_ISCHR(mode))
s = strdup("/run/systemd/inaccessible/chr");
else if (S_ISBLK(mode))
s = strdup("/run/systemd/inaccessible/blk");
else
return -ENODEV;
if (!s)
return -ENOMEM;
*ret = s;
return 0;
}
r = device_path_make_major_minor(mode, devno, &p);
if (r < 0)
return r;
return chase_symlinks(p, NULL, 0, ret, NULL);
}
int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret_devno) {
mode_t mode;
dev_t devno;
int r;
/* Tries to extract the major/minor directly from the device path if we can. Handles /dev/block/ and /dev/char/
* paths, as well out synthetic inaccessible device nodes. Never goes to disk. Returns -ENODEV if the device
* path cannot be parsed like this. */
if (path_equal(path, "/run/systemd/inaccessible/chr")) {
mode = S_IFCHR;
devno = makedev(0, 0);
} else if (path_equal(path, "/run/systemd/inaccessible/blk")) {
mode = S_IFBLK;
devno = makedev(0, 0);
} else {
const char *w;
w = path_startswith(path, "/dev/block/");
if (w)
mode = S_IFBLK;
else {
w = path_startswith(path, "/dev/char/");
if (!w)
return -ENODEV;
mode = S_IFCHR;
}
r = parse_dev(w, &devno);
if (r < 0)
return r;
}
if (ret_mode)
*ret_mode = mode;
if (ret_devno)
*ret_devno = devno;
return 0;
}
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