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systemd/src/udev/udev-node.c
Lennart Poettering 35cd0ba516 shared: clean up mkdir.h/label.h situation 
Previously the mkdir_label() family of calls was implemented in
src/shared/mkdir-label.c but its functions partly declared ins
src/shared/label.h and partly in src/basic/mkdir.h (!!). That's weird
(and wrong).

Let's clean this up, and add a proper mkdir-label.h matching the .c
file.
2021-11-16 17:03:28 +01:00

720 lines
27 KiB
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/* SPDX-License-Identifier: GPL-2.0-or-later */
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stddef.h>
#include <sys/stat.h>
#include <unistd.h>
#include "sd-id128.h"
#include "alloc-util.h"
#include "device-private.h"
#include "device-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "format-util.h"
#include "fs-util.h"
#include "hexdecoct.h"
#include "mkdir-label.h"
#include "parse-util.h"
#include "path-util.h"
#include "random-util.h"
#include "selinux-util.h"
#include "smack-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strxcpyx.h"
#include "time-util.h"
#include "udev-node.h"
#include "user-util.h"
#define CREATE_LINK_MAX_RETRIES 128
#define LINK_UPDATE_MAX_RETRIES 128
#define CREATE_STACK_LINK_MAX_RETRIES 128
#define UPDATE_TIMESTAMP_MAX_RETRIES 128
#define MAX_RANDOM_DELAY (250 * USEC_PER_MSEC)
#define MIN_RANDOM_DELAY ( 50 * USEC_PER_MSEC)
#define UDEV_NODE_HASH_KEY SD_ID128_MAKE(b9,6a,f1,ce,40,31,44,1a,9e,19,ec,8b,ae,f3,e3,2f)
static int create_symlink(const char *target, const char *slink) {
int r;
assert(target);
assert(slink);
for (unsigned i = 0; i < CREATE_LINK_MAX_RETRIES; i++) {
r = mkdir_parents_label(slink, 0755);
if (r == -ENOENT)
continue;
if (r < 0)
return r;
mac_selinux_create_file_prepare(slink, S_IFLNK);
r = RET_NERRNO(symlink(target, slink));
mac_selinux_create_file_clear();
if (r != -ENOENT)
return r;
}
return r;
}
static int node_symlink(sd_device *dev, const char *node, const char *slink) {
_cleanup_free_ char *slink_dirname = NULL, *target = NULL;
const char *id, *slink_tmp;
struct stat stats;
int r;
assert(dev);
assert(node);
assert(slink);
if (lstat(slink, &stats) >= 0) {
if (!S_ISLNK(stats.st_mode))
return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EEXIST),
"Conflicting inode '%s' found, link to '%s' will not be created.", slink, node);
} else if (errno != ENOENT)
return log_device_debug_errno(dev, errno, "Failed to lstat() '%s': %m", slink);
r = path_extract_directory(slink, &slink_dirname);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get parent directory of '%s': %m", slink);
/* use relative link */
r = path_make_relative(slink_dirname, node, &target);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get relative path from '%s' to '%s': %m", slink, node);
r = device_get_device_id(dev, &id);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device id: %m");
slink_tmp = strjoina(slink, ".tmp-", id);
(void) unlink(slink_tmp);
r = create_symlink(target, slink_tmp);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to create symlink '%s' to '%s': %m", slink_tmp, target);
if (rename(slink_tmp, slink) < 0) {
r = log_device_debug_errno(dev, errno, "Failed to rename '%s' to '%s': %m", slink_tmp, slink);
(void) unlink(slink_tmp);
return r;
}
return 0;
}
static int link_find_prioritized(sd_device *dev, bool add, const char *stackdir, char **ret) {
_cleanup_closedir_ DIR *dir = NULL;
_cleanup_free_ char *target = NULL;
struct dirent *dent;
int r, priority = 0;
const char *id;
assert(dev);
assert(stackdir);
assert(ret);
/* Find device node of device with highest priority. This returns 1 if a device found, 0 if no
* device found, or a negative errno. */
if (add) {
const char *devnode;
r = device_get_devlink_priority(dev, &priority);
if (r < 0)
return r;
r = sd_device_get_devname(dev, &devnode);
if (r < 0)
return r;
target = strdup(devnode);
if (!target)
return -ENOMEM;
}
dir = opendir(stackdir);
if (!dir) {
if (add) /* The stack directory must exist. */
return -errno;
if (errno != ENOENT)
return -errno;
*ret = NULL;
return 0;
}
r = device_get_device_id(dev, &id);
if (r < 0)
return r;
FOREACH_DIRENT_ALL(dent, dir, break) {
_cleanup_free_ char *path = NULL, *buf = NULL;
int tmp_prio;
if (dent->d_name[0] == '.')
continue;
/* skip ourself */
if (streq(dent->d_name, id))
continue;
path = path_join(stackdir, dent->d_name);
if (!path)
return -ENOMEM;
if (readlink_malloc(path, &buf) >= 0) {
char *devnode;
/* New format. The devnode and priority can be obtained from symlink. */
devnode = strchr(buf, ':');
if (!devnode || devnode == buf)
continue;
*(devnode++) = '\0';
if (!path_startswith(devnode, "/dev"))
continue;
if (safe_atoi(buf, &tmp_prio) < 0)
continue;
if (target && tmp_prio <= priority)
continue;
r = free_and_strdup(&target, devnode);
if (r < 0)
return r;
} else {
_cleanup_(sd_device_unrefp) sd_device *tmp_dev = NULL;
const char *devnode;
/* Old format. The devnode and priority must be obtained from uevent and
* udev database files. */
if (sd_device_new_from_device_id(&tmp_dev, dent->d_name) < 0)
continue;
if (device_get_devlink_priority(tmp_dev, &tmp_prio) < 0)
continue;
if (target && tmp_prio <= priority)
continue;
if (sd_device_get_devname(tmp_dev, &devnode) < 0)
continue;
r = free_and_strdup(&target, devnode);
if (r < 0)
return r;
}
priority = tmp_prio;
}
*ret = TAKE_PTR(target);
return !!*ret;
}
size_t udev_node_escape_path(const char *src, char *dest, size_t size) {
size_t i, j;
uint64_t h;
assert(src);
assert(dest);
assert(size >= 12);
for (i = 0, j = 0; src[i] != '\0'; i++) {
if (src[i] == '/') {
if (j+4 >= size - 12 + 1)
goto toolong;
memcpy(&dest[j], "\\x2f", 4);
j += 4;
} else if (src[i] == '\\') {
if (j+4 >= size - 12 + 1)
goto toolong;
memcpy(&dest[j], "\\x5c", 4);
j += 4;
} else {
if (j+1 >= size - 12 + 1)
goto toolong;
dest[j] = src[i];
j++;
}
}
dest[j] = '\0';
return j;
toolong:
/* If the input path is too long to encode as a filename, then let's suffix with a string
* generated from the hash of the path. */
h = siphash24_string(src, UDEV_NODE_HASH_KEY.bytes);
for (unsigned k = 0; k <= 10; k++)
dest[size - k - 2] = urlsafe_base64char((h >> (k * 6)) & 63);
dest[size - 1] = '\0';
return size - 1;
}
static int update_timestamp(sd_device *dev, const char *path, struct stat *prev) {
assert(path);
assert(prev);
/* Even if a symlink in the stack directory is created/removed, the mtime of the directory may
* not be changed. Why? Let's consider the following situation. For simplicity, let's assume
* there exist two udev workers (A and B) and all of them calls link_update() for the same
* devlink simultaneously.
*
* 1. A creates/removes a symlink in the stack directory.
* 2. A calls the first stat() in the loop of link_update().
* 3. A calls link_find_prioritized().
* 4. B creates/removes another symlink in the stack directory, so the result of the step 3 is outdated.
* 5. B finishes link_update().
* 6. A creates/removes devlink according to the outdated result in the step 3.
* 7. A calls the second stat() in the loop of link_update().
*
* If these 7 steps are processed in this order within a short time period that kernel's timer
* does not increase, then even if the contents in the stack directory is changed, the results
* of two stat() called by A shows the same timestamp, and A cannot detect the change.
*
* By calling this function after creating/removing symlinks in the stack directory, the
* timestamp of the stack directory is always increased at least in the above step 5, so A can
* detect the update. */
if ((prev->st_mode & S_IFMT) == 0)
return 0; /* Does not exist, or previous stat() failed. */
for (unsigned i = 0; i < UPDATE_TIMESTAMP_MAX_RETRIES; i++) {
struct stat st;
if (stat(path, &st) < 0)
return -errno;
if (!stat_inode_unmodified(prev, &st))
return 0;
log_device_debug(dev,
"%s is modified, but its timestamp is not changed, "
"updating timestamp after 10ms.",
path);
(void) usleep(10 * USEC_PER_MSEC);
if (utimensat(AT_FDCWD, path, NULL, 0) < 0)
return -errno;
}
return -ELOOP;
}
static int update_stack_directory(sd_device *dev, const char *dirname, bool add) {
_cleanup_free_ char *filename = NULL, *data = NULL, *buf = NULL;
const char *devname, *id;
struct stat st = {};
int priority, r;
assert(dev);
assert(dirname);
r = device_get_device_id(dev, &id);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device id: %m");
filename = path_join(dirname, id);
if (!filename)
return log_oom_debug();
if (!add) {
int unlink_error = 0, stat_error = 0;
if (stat(dirname, &st) < 0) {
if (errno == ENOENT)
return 0; /* The stack directory is already removed. That's OK. */
stat_error = -errno;
}
if (unlink(filename) < 0)
unlink_error = -errno;
if (rmdir(dirname) >= 0 || errno == ENOENT)
return 0;
if (unlink_error < 0) {
if (unlink_error == -ENOENT)
return 0;
/* If we failed to remove the symlink, then there is almost nothing we can do. */
return log_device_debug_errno(dev, unlink_error, "Failed to remove %s: %m", filename);
}
if (stat_error < 0)
return log_device_debug_errno(dev, stat_error, "Failed to stat %s: %m", dirname);
/* The symlink was removed. Check if the timestamp of directory is changed. */
r = update_timestamp(dev, dirname, &st);
if (r < 0 && r != -ENOENT)
return log_device_debug_errno(dev, r, "Failed to update timestamp of %s: %m", dirname);
return 0;
}
r = sd_device_get_devname(dev, &devname);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device node: %m");
r = device_get_devlink_priority(dev, &priority);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get priority of device node symlink: %m");
if (asprintf(&data, "%i:%s", priority, devname) < 0)
return log_oom_debug();
if (readlink_malloc(filename, &buf) >= 0 && streq(buf, data))
return 0;
if (unlink(filename) < 0 && errno != ENOENT)
log_device_debug_errno(dev, errno, "Failed to remove %s, ignoring: %m", filename);
for (unsigned j = 0; j < CREATE_STACK_LINK_MAX_RETRIES; j++) {
/* This may fail with -ENOENT when the parent directory is removed during
* creating the file by another udevd worker. */
r = mkdir_p(dirname, 0755);
if (r == -ENOENT)
continue;
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to create directory %s: %m", dirname);
if (stat(dirname, &st) < 0) {
if (errno == ENOENT)
continue;
return log_device_debug_errno(dev, errno, "Failed to stat %s: %m", dirname);
}
if (symlink(data, filename) < 0) {
if (errno == ENOENT)
continue;
return log_device_debug_errno(dev, errno, "Failed to create symbolic link %s: %m", filename);
}
/* The symlink was created. Check if the timestamp of directory is changed. */
r = update_timestamp(dev, dirname, &st);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to update timestamp of %s: %m", dirname);
return 0;
}
return log_device_debug_errno(dev, SYNTHETIC_ERRNO(ELOOP), "Failed to create symbolic link %s: %m", filename);
}
/* manage "stack of names" with possibly specified device priorities */
static int link_update(sd_device *dev, const char *slink_in, bool add) {
_cleanup_free_ char *slink = NULL, *dirname = NULL;
const char *slink_name;
char name_enc[NAME_MAX+1];
int r;
assert(dev);
assert(slink_in);
slink = strdup(slink_in);
if (!slink)
return log_oom_debug();
path_simplify(slink);
slink_name = path_startswith(slink, "/dev");
if (!slink_name ||
empty_or_root(slink_name) ||
!path_is_normalized(slink_name))
return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),
"Invalid symbolic link of device node: %s", slink);
(void) udev_node_escape_path(slink_name, name_enc, sizeof(name_enc));
dirname = path_join("/run/udev/links", name_enc);
if (!dirname)
return log_oom_debug();
r = update_stack_directory(dev, dirname, add);
if (r < 0)
return r;
for (unsigned i = 0; i < LINK_UPDATE_MAX_RETRIES; i++) {
_cleanup_free_ char *target = NULL;
struct stat st1 = {}, st2 = {};
if (i > 0) {
usec_t delay = MIN_RANDOM_DELAY + random_u64_range(MAX_RANDOM_DELAY - MIN_RANDOM_DELAY);
log_device_debug(dev, "Directory %s was updated, retrying to update devlink %s after %s.",
dirname, slink, FORMAT_TIMESPAN(delay, USEC_PER_MSEC));
(void) usleep(delay);
}
if (stat(dirname, &st1) < 0 && errno != ENOENT)
return log_device_debug_errno(dev, errno, "Failed to stat %s: %m", dirname);
r = link_find_prioritized(dev, add, dirname, &target);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to determine device node with the highest priority for '%s': %m", slink);
if (r == 0) {
log_device_debug(dev, "No reference left for '%s', removing", slink);
if (unlink(slink) < 0 && errno != ENOENT)
log_device_debug_errno(dev, errno, "Failed to remove '%s', ignoring: %m", slink);
(void) rmdir_parents(slink, "/dev");
return 0;
}
r = node_symlink(dev, target, slink);
if (r < 0)
return r;
if (stat(dirname, &st2) < 0 && errno != ENOENT)
return log_device_debug_errno(dev, errno, "Failed to stat %s: %m", dirname);
if (((st1.st_mode & S_IFMT) == 0 && (st2.st_mode & S_IFMT) == 0) ||
stat_inode_unmodified(&st1, &st2))
return 0;
}
return -ELOOP;
}
static int device_get_devpath_by_devnum(sd_device *dev, char **ret) {
const char *subsystem;
dev_t devnum;
int r;
assert(dev);
assert(ret);
r = sd_device_get_subsystem(dev, &subsystem);
if (r < 0)
return r;
r = sd_device_get_devnum(dev, &devnum);
if (r < 0)
return r;
return device_path_make_major_minor(streq(subsystem, "block") ? S_IFBLK : S_IFCHR, devnum, ret);
}
int udev_node_update(sd_device *dev, sd_device *dev_old) {
_cleanup_free_ char *filename = NULL;
const char *devnode, *devlink;
int r;
assert(dev);
assert(dev_old);
r = sd_device_get_devname(dev, &devnode);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get devnode: %m");
if (DEBUG_LOGGING) {
const char *id = NULL;
(void) device_get_device_id(dev, &id);
log_device_debug(dev, "Handling device node '%s', devnum=%s", devnode, strna(id));
}
/* update possible left-over symlinks */
FOREACH_DEVICE_DEVLINK(dev_old, devlink) {
/* check if old link name still belongs to this device */
if (device_has_devlink(dev, devlink))
continue;
log_device_debug(dev,
"Removing/updating old device symlink '%s', which is no longer belonging to this device.",
devlink);
r = link_update(dev, devlink, /* add = */ false);
if (r < 0)
log_device_warning_errno(dev, r,
"Failed to remove/update device symlink '%s', ignoring: %m",
devlink);
}
/* create/update symlinks, add symlinks to name index */
FOREACH_DEVICE_DEVLINK(dev, devlink) {
r = link_update(dev, devlink, /* add = */ true);
if (r < 0)
log_device_warning_errno(dev, r,
"Failed to create/update device symlink '%s', ignoring: %m",
devlink);
}
r = device_get_devpath_by_devnum(dev, &filename);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device path: %m");
/* always add /dev/{block,char}/$major:$minor */
r = node_symlink(dev, devnode, filename);
if (r < 0)
return log_device_warning_errno(dev, r, "Failed to create device symlink '%s': %m", filename);
return 0;
}
int udev_node_remove(sd_device *dev) {
_cleanup_free_ char *filename = NULL;
const char *devlink;
int r;
assert(dev);
/* remove/update symlinks, remove symlinks from name index */
FOREACH_DEVICE_DEVLINK(dev, devlink) {
r = link_update(dev, devlink, /* add = */ false);
if (r < 0)
log_device_warning_errno(dev, r,
"Failed to remove/update device symlink '%s', ignoring: %m",
devlink);
}
r = device_get_devpath_by_devnum(dev, &filename);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device path: %m");
/* remove /dev/{block,char}/$major:$minor */
if (unlink(filename) < 0 && errno != ENOENT)
return log_device_debug_errno(dev, errno, "Failed to remove '%s': %m", filename);
return 0;
}
int udev_node_apply_permissions(
sd_device *dev,
bool apply_mac,
mode_t mode,
uid_t uid,
gid_t gid,
OrderedHashmap *seclabel_list) {
const char *devnode, *subsystem, *id = NULL;
bool apply_mode, apply_uid, apply_gid;
_cleanup_close_ int node_fd = -1;
struct stat stats;
dev_t devnum;
int r;
assert(dev);
r = sd_device_get_devname(dev, &devnode);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get devname: %m");
r = sd_device_get_subsystem(dev, &subsystem);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get subsystem: %m");
r = sd_device_get_devnum(dev, &devnum);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get devnum: %m");
(void) device_get_device_id(dev, &id);
if (streq(subsystem, "block"))
mode |= S_IFBLK;
else
mode |= S_IFCHR;
node_fd = open(devnode, O_PATH|O_NOFOLLOW|O_CLOEXEC);
if (node_fd < 0) {
if (errno == ENOENT) {
log_device_debug_errno(dev, errno, "Device node %s is missing, skipping handling.", devnode);
return 0; /* This is necessarily racey, so ignore missing the device */
}
return log_device_debug_errno(dev, errno, "Cannot open node %s: %m", devnode);
}
if (fstat(node_fd, &stats) < 0)
return log_device_debug_errno(dev, errno, "cannot stat() node %s: %m", devnode);
if ((mode != MODE_INVALID && (stats.st_mode & S_IFMT) != (mode & S_IFMT)) || stats.st_rdev != devnum) {
log_device_debug(dev, "Found node '%s' with non-matching devnum %s, skipping handling.",
devnode, strna(id));
return 0; /* We might process a device that already got replaced by the time we have a look
* at it, handle this gracefully and step away. */
}
apply_mode = mode != MODE_INVALID && (stats.st_mode & 0777) != (mode & 0777);
apply_uid = uid_is_valid(uid) && stats.st_uid != uid;
apply_gid = gid_is_valid(gid) && stats.st_gid != gid;
if (apply_mode || apply_uid || apply_gid || apply_mac) {
bool selinux = false, smack = false;
const char *name, *label;
if (apply_mode || apply_uid || apply_gid) {
log_device_debug(dev, "Setting permissions %s, uid=" UID_FMT ", gid=" GID_FMT ", mode=%#o",
devnode,
uid_is_valid(uid) ? uid : stats.st_uid,
gid_is_valid(gid) ? gid : stats.st_gid,
mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777);
r = fchmod_and_chown(node_fd, mode, uid, gid);
if (r < 0)
log_device_full_errno(dev, r == -ENOENT ? LOG_DEBUG : LOG_ERR, r,
"Failed to set owner/mode of %s to uid=" UID_FMT
", gid=" GID_FMT ", mode=%#o: %m",
devnode,
uid_is_valid(uid) ? uid : stats.st_uid,
gid_is_valid(gid) ? gid : stats.st_gid,
mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777);
} else
log_device_debug(dev, "Preserve permissions of %s, uid=" UID_FMT ", gid=" GID_FMT ", mode=%#o",
devnode,
uid_is_valid(uid) ? uid : stats.st_uid,
gid_is_valid(gid) ? gid : stats.st_gid,
mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777);
/* apply SECLABEL{$module}=$label */
ORDERED_HASHMAP_FOREACH_KEY(label, name, seclabel_list) {
int q;
if (streq(name, "selinux")) {
selinux = true;
q = mac_selinux_apply_fd(node_fd, devnode, label);
if (q < 0)
log_device_full_errno(dev, q == -ENOENT ? LOG_DEBUG : LOG_ERR, q,
"SECLABEL: failed to set SELinux label '%s': %m", label);
else
log_device_debug(dev, "SECLABEL: set SELinux label '%s'", label);
} else if (streq(name, "smack")) {
smack = true;
q = mac_smack_apply_fd(node_fd, SMACK_ATTR_ACCESS, label);
if (q < 0)
log_device_full_errno(dev, q == -ENOENT ? LOG_DEBUG : LOG_ERR, q,
"SECLABEL: failed to set SMACK label '%s': %m", label);
else
log_device_debug(dev, "SECLABEL: set SMACK label '%s'", label);
} else
log_device_error(dev, "SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label);
}
/* set the defaults */
if (!selinux)
(void) mac_selinux_fix_fd(node_fd, devnode, LABEL_IGNORE_ENOENT);
if (!smack)
(void) mac_smack_apply_fd(node_fd, SMACK_ATTR_ACCESS, NULL);
}
/* always update timestamp when we re-use the node, like on media change events */
r = futimens_opath(node_fd, NULL);
if (r < 0)
log_device_debug_errno(dev, r, "Failed to adjust timestamp of node %s: %m", devnode);
return 0;
}
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