path: root/src/shared/udev-util.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <unistd.h>

#include "alloc-util.h"
#include "device-util.h"
#include "env-file.h"
#include "escape.h"
#include "log.h"
#include "macro.h"
#include "parse-util.h"
#include "path-util.h"
#include "signal-util.h"
#include "string-table.h"
#include "string-util.h"
#include "udev-util.h"
#include "utf8.h"

static const char* const resolve_name_timing_table[_RESOLVE_NAME_TIMING_MAX] = {
        [RESOLVE_NAME_NEVER] = "never",
        [RESOLVE_NAME_LATE] = "late",
        [RESOLVE_NAME_EARLY] = "early",
};

DEFINE_STRING_TABLE_LOOKUP(resolve_name_timing, ResolveNameTiming);

int udev_parse_config_full(
                unsigned *ret_children_max,
                usec_t *ret_exec_delay_usec,
                usec_t *ret_event_timeout_usec,
                ResolveNameTiming *ret_resolve_name_timing,
                int *ret_timeout_signal) {

        _cleanup_free_ char *log_val = NULL, *children_max = NULL, *exec_delay = NULL, *event_timeout = NULL, *resolve_names = NULL, *timeout_signal = NULL;
        int r;

        r = parse_env_file(NULL, "/etc/udev/udev.conf",
                           "udev_log", &log_val,
                           "children_max", &children_max,
                           "exec_delay", &exec_delay,
                           "event_timeout", &event_timeout,
                           "resolve_names", &resolve_names,
                           "timeout_signal", &timeout_signal);
        if (r == -ENOENT)
                return 0;
        if (r < 0)
                return r;

        if (log_val) {
                const char *log;
                size_t n;

                /* unquote */
                n = strlen(log_val);
                if (n >= 2 &&
                    ((log_val[0] == '"' && log_val[n-1] == '"') ||
                     (log_val[0] == '\'' && log_val[n-1] == '\''))) {
                        log_val[n - 1] = '\0';
                        log = log_val + 1;
                } else
                        log = log_val;

                /* we set the udev log level here explicitly, this is supposed
                 * to regulate the code in libudev/ and udev/. */
                r = log_set_max_level_from_string_realm(LOG_REALM_UDEV, log);
                if (r < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to set udev log level '%s', ignoring: %m", log);
        }

        if (ret_children_max && children_max) {
                r = safe_atou(children_max, ret_children_max);
                if (r < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to parse children_max=%s, ignoring: %m", children_max);
        }

        if (ret_exec_delay_usec && exec_delay) {
                r = parse_sec(exec_delay, ret_exec_delay_usec);
                if (r < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to parse exec_delay=%s, ignoring: %m", exec_delay);
        }

        if (ret_event_timeout_usec && event_timeout) {
                r = parse_sec(event_timeout, ret_event_timeout_usec);
                if (r < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to parse event_timeout=%s, ignoring: %m", event_timeout);
        }

        if (ret_resolve_name_timing && resolve_names) {
                ResolveNameTiming t;

                t = resolve_name_timing_from_string(resolve_names);
                if (t < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to parse resolve_names=%s, ignoring.", resolve_names);
                else
                        *ret_resolve_name_timing = t;
        }

        if (ret_timeout_signal && timeout_signal) {
                r = signal_from_string(timeout_signal);
                if (r < 0)
                        log_syntax(NULL, LOG_WARNING, "/etc/udev/udev.conf", 0, r,
                                   "failed to parse timeout_signal=%s, ignoring: %m", timeout_signal);
                else
                        *ret_timeout_signal = r;
        }

        return 0;
}

/* Note that if -ENOENT is returned, it will be logged at debug level rather than error,
 * because it's an expected, common occurrence that the caller will handle with a fallback */
static int device_new_from_dev_path(const char *devlink, sd_device **ret_device) {
        struct stat st;
        int r;

        assert(devlink);

        if (stat(devlink, &st) < 0)
                return log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_ERR, errno,
                                      "Failed to stat() %s: %m", devlink);

        if (!S_ISBLK(st.st_mode))
                return log_error_errno(SYNTHETIC_ERRNO(ENOTBLK),
                                       "%s does not point to a block device: %m", devlink);

        r = sd_device_new_from_devnum(ret_device, 'b', st.st_rdev);
        if (r < 0)
                return log_error_errno(r, "Failed to initialize device from %s: %m", devlink);

        return 0;
}

struct DeviceMonitorData {
        const char *sysname;
        const char *devlink;
        sd_device *device;
};

static void device_monitor_data_free(struct DeviceMonitorData *d) {
        assert(d);

        sd_device_unref(d->device);
}

static int device_monitor_handler(sd_device_monitor *monitor, sd_device *device, void *userdata) {
        struct DeviceMonitorData *data = userdata;
        const char *sysname;

        assert(device);
        assert(data);
        assert(data->sysname || data->devlink);
        assert(!data->device);

        /* Ignore REMOVE events here. We are waiting for initialization after all, not de-initialization. We
         * might see a REMOVE event from an earlier use of the device (devices by the same name are recycled
         * by the kernel after all), which we should not get confused by. After all we cannot distinguish use
         * cycles of the devices, as the udev queue is entirely asynchronous.
         *
         * If we see a REMOVE event here for the use cycle we actually care about then we won't notice of
         * course, but that should be OK, given the timeout logic used on the wait loop: this will be noticed
         * by means of -ETIMEDOUT. Thus we won't notice immediately, but eventually, and that should be
         * sufficient for an error path that should regularly not happen.
         *
         * (And yes, we only need to special case REMOVE. It's the only "negative" event type, where a device
         * ceases to exist. All other event types are "positive": the device exists and is registered in the
         * udev database, thus whenever we see the event, we can consider it initialized.) */
        if (device_for_action(device, DEVICE_ACTION_REMOVE))
                return 0;

        if (data->sysname && sd_device_get_sysname(device, &sysname) >= 0 && streq(sysname, data->sysname))
                goto found;

        if (data->devlink) {
                const char *devlink;

                FOREACH_DEVICE_DEVLINK(device, devlink)
                        if (path_equal(devlink, data->devlink))
                                goto found;

                if (sd_device_get_devname(device, &devlink) >= 0 && path_equal(devlink, data->devlink))
                        goto found;
        }

        return 0;

found:
        data->device = sd_device_ref(device);
        return sd_event_exit(sd_device_monitor_get_event(monitor), 0);
}

static int device_wait_for_initialization_internal(
                sd_device *_device,
                const char *devlink,
                const char *subsystem,
                usec_t deadline,
                sd_device **ret) {

        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor = NULL;
        _cleanup_(sd_event_source_unrefp) sd_event_source *timeout_source = NULL;
        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
        /* Ensure that if !_device && devlink, device gets unrefd on errors since it will be new */
        _cleanup_(sd_device_unrefp) sd_device *device = sd_device_ref(_device);
        _cleanup_(device_monitor_data_free) struct DeviceMonitorData data = {
                .devlink = devlink,
        };
        int r;

        assert(device || (subsystem && devlink));

        /* Devlink might already exist, if it does get the device to use the sysname filtering */
        if (!device && devlink) {
                r = device_new_from_dev_path(devlink, &device);
                if (r < 0 && r != -ENOENT)
                        return r;
        }

        if (device) {
                if (sd_device_get_is_initialized(device) > 0) {
                        if (ret)
                                *ret = sd_device_ref(device);
                        return 0;
                }
                /* We need either the sysname or the devlink for filtering */
                assert_se(sd_device_get_sysname(device, &data.sysname) >= 0 || devlink);
        }

        /* Wait until the device is initialized, so that we can get access to the ID_PATH property */

        r = sd_event_new(&event);
        if (r < 0)
                return log_error_errno(r, "Failed to get default event: %m");

        r = sd_device_monitor_new(&monitor);
        if (r < 0)
                return log_error_errno(r, "Failed to acquire monitor: %m");

        if (device && !subsystem) {
                r = sd_device_get_subsystem(device, &subsystem);
                if (r < 0 && r != -ENOENT)
                        return log_device_error_errno(device, r, "Failed to get subsystem: %m");
        }

        if (subsystem) {
                r = sd_device_monitor_filter_add_match_subsystem_devtype(monitor, subsystem, NULL);
                if (r < 0)
                        return log_error_errno(r, "Failed to add %s subsystem match to monitor: %m", subsystem);
        }

        r = sd_device_monitor_attach_event(monitor, event);
        if (r < 0)
                return log_error_errno(r, "Failed to attach event to device monitor: %m");

        r = sd_device_monitor_start(monitor, device_monitor_handler, &data);
        if (r < 0)
                return log_error_errno(r, "Failed to start device monitor: %m");

        if (deadline != USEC_INFINITY) {
                r = sd_event_add_time(
                                event, &timeout_source,
                                CLOCK_MONOTONIC, deadline, 0,
                                NULL, INT_TO_PTR(-ETIMEDOUT));
                if (r < 0)
                        return log_error_errno(r, "Failed to add timeout event source: %m");
        }

        /* Check again, maybe things changed. Udev will re-read the db if the device wasn't initialized
         * yet. */
        if (!device && devlink) {
                r = device_new_from_dev_path(devlink, &device);
                if (r < 0 && r != -ENOENT)
                        return r;
        }
        if (device && sd_device_get_is_initialized(device) > 0) {
                if (ret)
                        *ret = sd_device_ref(device);
                return 0;
        }

        r = sd_event_loop(event);
        if (r < 0)
                return log_error_errno(r, "Failed to wait for device to be initialized: %m");

        if (ret)
                *ret = TAKE_PTR(data.device);
        return 0;
}

int device_wait_for_initialization(sd_device *device, const char *subsystem, usec_t deadline, sd_device **ret) {
        return device_wait_for_initialization_internal(device, NULL, subsystem, deadline, ret);
}

int device_wait_for_devlink(const char *devlink, const char *subsystem, usec_t deadline, sd_device **ret) {
        return device_wait_for_initialization_internal(NULL, devlink, subsystem, deadline, ret);
}

int device_is_renaming(sd_device *dev) {
        int r;

        assert(dev);

        r = sd_device_get_property_value(dev, "ID_RENAMING", NULL);
        if (r == -ENOENT)
                return false;
        if (r < 0)
                return r;

        return true;
}

bool device_for_action(sd_device *dev, DeviceAction action) {
        DeviceAction a;

        assert(dev);

        if (device_get_action(dev, &a) < 0)
                return false;

        return a == action;
}

int udev_rule_parse_value(char *str, char **ret_value, char **ret_endpos) {
        char *i, *j;
        int r;
        bool is_escaped;

        /* value must be double quotated */
        is_escaped = str[0] == 'e';
        str += is_escaped;
        if (str[0] != '"')
                return -EINVAL;
        str++;

        if (!is_escaped) {
                /* unescape double quotation '\"'->'"' */
                for (i = j = str; *i != '"'; i++, j++) {
                        if (*i == '\0')
                                return -EINVAL;
                        if (i[0] == '\\' && i[1] == '"')
                                i++;
                        *j = *i;
                }
                j[0] = '\0';
        } else {
                _cleanup_free_ char *unescaped = NULL;

                /* find the end position of value */
                for (i = str; *i != '"'; i++) {
                        if (i[0] == '\\')
                                i++;
                        if (*i == '\0')
                                return -EINVAL;
                }
                i[0] = '\0';

                r = cunescape_length(str, i - str, 0, &unescaped);
                if (r < 0)
                        return r;
                assert(r <= i - str);
                memcpy(str, unescaped, r + 1);
        }

        *ret_value = str;
        *ret_endpos = i + 1;
        return 0;
}