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Systemd/src/core/path.c
Lennart Poettering 47ab8f73e3 core: propagate unit start limit hit state to triggering path unit 
We already do this for socket and automount units, do it for path units
too: if the triggered service keeps hitting the start limit, then fail
the triggering unit too, so that we don#t busy loop forever.

(Note that this leaves only timer units out in the cold for this kind of
protection, but it shouldn't matter there, as they are naturally
protected against busy loops: they are scheduled by time anyway).

Fixes: #16669
2020-09-14 13:05:09 +02:00

847 lines
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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <sys/epoll.h>
#include <sys/inotify.h>
#include <unistd.h>
#include "bus-error.h"
#include "bus-util.h"
#include "dbus-path.h"
#include "dbus-unit.h"
#include "escape.h"
#include "fd-util.h"
#include "fs-util.h"
#include "glob-util.h"
#include "macro.h"
#include "mkdir.h"
#include "path.h"
#include "path-util.h"
#include "serialize.h"
#include "special.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "unit-name.h"
#include "unit.h"
static const UnitActiveState state_translation_table[_PATH_STATE_MAX] = {
[PATH_DEAD] = UNIT_INACTIVE,
[PATH_WAITING] = UNIT_ACTIVE,
[PATH_RUNNING] = UNIT_ACTIVE,
[PATH_FAILED] = UNIT_FAILED,
};
static int path_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata);
int path_spec_watch(PathSpec *s, sd_event_io_handler_t handler) {
static const int flags_table[_PATH_TYPE_MAX] = {
[PATH_EXISTS] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB,
[PATH_EXISTS_GLOB] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB,
[PATH_CHANGED] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO,
[PATH_MODIFIED] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO|IN_MODIFY,
[PATH_DIRECTORY_NOT_EMPTY] = IN_DELETE_SELF|IN_MOVE_SELF|IN_ATTRIB|IN_CREATE|IN_MOVED_TO,
};
bool exists = false;
char *slash, *oldslash = NULL;
int r;
assert(s);
assert(s->unit);
assert(handler);
path_spec_unwatch(s);
s->inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
if (s->inotify_fd < 0) {
r = -errno;
goto fail;
}
r = sd_event_add_io(s->unit->manager->event, &s->event_source, s->inotify_fd, EPOLLIN, handler, s);
if (r < 0)
goto fail;
(void) sd_event_source_set_description(s->event_source, "path");
/* This function assumes the path was passed through path_simplify()! */
assert(!strstr(s->path, "//"));
for (slash = strchr(s->path, '/'); ; slash = strchr(slash+1, '/')) {
char *cut = NULL;
int flags;
char tmp;
if (slash) {
cut = slash + (slash == s->path);
tmp = *cut;
*cut = '\0';
flags = IN_MOVE_SELF | IN_DELETE_SELF | IN_ATTRIB | IN_CREATE | IN_MOVED_TO;
} else
flags = flags_table[s->type];
r = inotify_add_watch(s->inotify_fd, s->path, flags);
if (r < 0) {
if (IN_SET(errno, EACCES, ENOENT)) {
if (cut)
*cut = tmp;
break;
}
/* This second call to inotify_add_watch() should fail like the previous
* one and is done for logging the error in a comprehensive way. */
r = inotify_add_watch_and_warn(s->inotify_fd, s->path, flags);
if (r < 0) {
if (cut)
*cut = tmp;
goto fail;
}
/* Hmm, we succeeded in adding the watch this time... let's continue. */
}
exists = true;
/* Path exists, we don't need to watch parent too closely. */
if (oldslash) {
char *cut2 = oldslash + (oldslash == s->path);
char tmp2 = *cut2;
*cut2 = '\0';
(void) inotify_add_watch(s->inotify_fd, s->path, IN_MOVE_SELF);
/* Error is ignored, the worst can happen is we get spurious events. */
*cut2 = tmp2;
}
if (cut)
*cut = tmp;
if (slash)
oldslash = slash;
else {
/* whole path has been iterated over */
s->primary_wd = r;
break;
}
}
if (!exists) {
r = log_error_errno(errno, "Failed to add watch on any of the components of %s: %m", s->path);
/* either EACCESS or ENOENT */
goto fail;
}
return 0;
fail:
path_spec_unwatch(s);
return r;
}
void path_spec_unwatch(PathSpec *s) {
assert(s);
s->event_source = sd_event_source_unref(s->event_source);
s->inotify_fd = safe_close(s->inotify_fd);
}
int path_spec_fd_event(PathSpec *s, uint32_t revents) {
union inotify_event_buffer buffer;
struct inotify_event *e;
ssize_t l;
int r = 0;
if (revents != EPOLLIN)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Got invalid poll event on inotify.");
l = read(s->inotify_fd, &buffer, sizeof(buffer));
if (l < 0) {
if (IN_SET(errno, EAGAIN, EINTR))
return 0;
return log_error_errno(errno, "Failed to read inotify event: %m");
}
FOREACH_INOTIFY_EVENT(e, buffer, l) {
if (IN_SET(s->type, PATH_CHANGED, PATH_MODIFIED) &&
s->primary_wd == e->wd)
r = 1;
}
return r;
}
static bool path_spec_check_good(PathSpec *s, bool initial, bool from_trigger_notify) {
bool b, good = false;
switch (s->type) {
case PATH_EXISTS:
good = access(s->path, F_OK) >= 0;
break;
case PATH_EXISTS_GLOB:
good = glob_exists(s->path) > 0;
break;
case PATH_DIRECTORY_NOT_EMPTY: {
int k;
k = dir_is_empty(s->path);
good = !(k == -ENOENT || k > 0);
break;
}
case PATH_CHANGED:
case PATH_MODIFIED:
b = access(s->path, F_OK) >= 0;
good = !initial && !from_trigger_notify && b != s->previous_exists;
s->previous_exists = b;
break;
default:
;
}
return good;
}
static void path_spec_mkdir(PathSpec *s, mode_t mode) {
int r;
if (IN_SET(s->type, PATH_EXISTS, PATH_EXISTS_GLOB))
return;
r = mkdir_p_label(s->path, mode);
if (r < 0)
log_warning_errno(r, "mkdir(%s) failed: %m", s->path);
}
static void path_spec_dump(PathSpec *s, FILE *f, const char *prefix) {
const char *type;
assert_se(type = path_type_to_string(s->type));
fprintf(f, "%s%s: %s\n", prefix, type, s->path);
}
void path_spec_done(PathSpec *s) {
assert(s);
assert(s->inotify_fd == -1);
free(s->path);
}
static void path_init(Unit *u) {
Path *p = PATH(u);
assert(u);
assert(u->load_state == UNIT_STUB);
p->directory_mode = 0755;
}
void path_free_specs(Path *p) {
PathSpec *s;
assert(p);
while ((s = p->specs)) {
path_spec_unwatch(s);
LIST_REMOVE(spec, p->specs, s);
path_spec_done(s);
free(s);
}
}
static void path_done(Unit *u) {
Path *p = PATH(u);
assert(p);
path_free_specs(p);
}
static int path_add_mount_dependencies(Path *p) {
PathSpec *s;
int r;
assert(p);
LIST_FOREACH(spec, s, p->specs) {
r = unit_require_mounts_for(UNIT(p), s->path, UNIT_DEPENDENCY_FILE);
if (r < 0)
return r;
}
return 0;
}
static int path_verify(Path *p) {
assert(p);
assert(UNIT(p)->load_state == UNIT_LOADED);
if (!p->specs) {
log_unit_error(UNIT(p), "Path unit lacks path setting. Refusing.");
return -ENOEXEC;
}
return 0;
}
static int path_add_default_dependencies(Path *p) {
int r;
assert(p);
if (!UNIT(p)->default_dependencies)
return 0;
r = unit_add_dependency_by_name(UNIT(p), UNIT_BEFORE, SPECIAL_PATHS_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
if (r < 0)
return r;
if (MANAGER_IS_SYSTEM(UNIT(p)->manager)) {
r = unit_add_two_dependencies_by_name(UNIT(p), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SYSINIT_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
if (r < 0)
return r;
}
return unit_add_two_dependencies_by_name(UNIT(p), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
}
static int path_add_trigger_dependencies(Path *p) {
Unit *x;
int r;
assert(p);
if (!hashmap_isempty(UNIT(p)->dependencies[UNIT_TRIGGERS]))
return 0;
r = unit_load_related_unit(UNIT(p), ".service", &x);
if (r < 0)
return r;
return unit_add_two_dependencies(UNIT(p), UNIT_BEFORE, UNIT_TRIGGERS, x, true, UNIT_DEPENDENCY_IMPLICIT);
}
static int path_add_extras(Path *p) {
int r;
r = path_add_trigger_dependencies(p);
if (r < 0)
return r;
r = path_add_mount_dependencies(p);
if (r < 0)
return r;
return path_add_default_dependencies(p);
}
static int path_load(Unit *u) {
Path *p = PATH(u);
int r;
assert(u);
assert(u->load_state == UNIT_STUB);
r = unit_load_fragment_and_dropin(u, true);
if (r < 0)
return r;
if (u->load_state != UNIT_LOADED)
return 0;
r = path_add_extras(p);
if (r < 0)
return r;
return path_verify(p);
}
static void path_dump(Unit *u, FILE *f, const char *prefix) {
Path *p = PATH(u);
Unit *trigger;
PathSpec *s;
assert(p);
assert(f);
trigger = UNIT_TRIGGER(u);
fprintf(f,
"%sPath State: %s\n"
"%sResult: %s\n"
"%sUnit: %s\n"
"%sMakeDirectory: %s\n"
"%sDirectoryMode: %04o\n",
prefix, path_state_to_string(p->state),
prefix, path_result_to_string(p->result),
prefix, trigger ? trigger->id : "n/a",
prefix, yes_no(p->make_directory),
prefix, p->directory_mode);
LIST_FOREACH(spec, s, p->specs)
path_spec_dump(s, f, prefix);
}
static void path_unwatch(Path *p) {
PathSpec *s;
assert(p);
LIST_FOREACH(spec, s, p->specs)
path_spec_unwatch(s);
}
static int path_watch(Path *p) {
int r;
PathSpec *s;
assert(p);
LIST_FOREACH(spec, s, p->specs) {
r = path_spec_watch(s, path_dispatch_io);
if (r < 0)
return r;
}
return 0;
}
static void path_set_state(Path *p, PathState state) {
PathState old_state;
assert(p);
if (p->state != state)
bus_unit_send_pending_change_signal(UNIT(p), false);
old_state = p->state;
p->state = state;
if (!IN_SET(state, PATH_WAITING, PATH_RUNNING))
path_unwatch(p);
if (state != old_state)
log_unit_debug(UNIT(p), "Changed %s -> %s", path_state_to_string(old_state), path_state_to_string(state));
unit_notify(UNIT(p), state_translation_table[old_state], state_translation_table[state], 0);
}
static void path_enter_waiting(Path *p, bool initial, bool from_trigger_notify);
static int path_coldplug(Unit *u) {
Path *p = PATH(u);
assert(p);
assert(p->state == PATH_DEAD);
if (p->deserialized_state != p->state) {
if (IN_SET(p->deserialized_state, PATH_WAITING, PATH_RUNNING))
path_enter_waiting(p, true, false);
else
path_set_state(p, p->deserialized_state);
}
return 0;
}
static void path_enter_dead(Path *p, PathResult f) {
assert(p);
if (p->result == PATH_SUCCESS)
p->result = f;
unit_log_result(UNIT(p), p->result == PATH_SUCCESS, path_result_to_string(p->result));
path_set_state(p, p->result != PATH_SUCCESS ? PATH_FAILED : PATH_DEAD);
}
static void path_enter_running(Path *p) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
Unit *trigger;
int r;
assert(p);
/* Don't start job if we are supposed to go down */
if (unit_stop_pending(UNIT(p)))
return;
trigger = UNIT_TRIGGER(UNIT(p));
if (!trigger) {
log_unit_error(UNIT(p), "Unit to trigger vanished.");
path_enter_dead(p, PATH_FAILURE_RESOURCES);
return;
}
r = manager_add_job(UNIT(p)->manager, JOB_START, trigger, JOB_REPLACE, NULL, &error, NULL);
if (r < 0)
goto fail;
path_set_state(p, PATH_RUNNING);
path_unwatch(p);
return;
fail:
log_unit_warning(UNIT(p), "Failed to queue unit startup job: %s", bus_error_message(&error, r));
path_enter_dead(p, PATH_FAILURE_RESOURCES);
}
static bool path_check_good(Path *p, bool initial, bool from_trigger_notify) {
PathSpec *s;
assert(p);
LIST_FOREACH(spec, s, p->specs)
if (path_spec_check_good(s, initial, from_trigger_notify))
return true;
return false;
}
static void path_enter_waiting(Path *p, bool initial, bool from_trigger_notify) {
Unit *trigger;
int r;
/* If the triggered unit is already running, so are we */
trigger = UNIT_TRIGGER(UNIT(p));
if (trigger && !UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(trigger))) {
path_set_state(p, PATH_RUNNING);
path_unwatch(p);
return;
}
if (path_check_good(p, initial, from_trigger_notify)) {
log_unit_debug(UNIT(p), "Got triggered.");
path_enter_running(p);
return;
}
r = path_watch(p);
if (r < 0)
goto fail;
/* Hmm, so now we have created inotify watches, but the file
* might have appeared/been removed by now, so we must
* recheck */
if (path_check_good(p, false, from_trigger_notify)) {
log_unit_debug(UNIT(p), "Got triggered.");
path_enter_running(p);
return;
}
path_set_state(p, PATH_WAITING);
return;
fail:
log_unit_warning_errno(UNIT(p), r, "Failed to enter waiting state: %m");
path_enter_dead(p, PATH_FAILURE_RESOURCES);
}
static void path_mkdir(Path *p) {
PathSpec *s;
assert(p);
if (!p->make_directory)
return;
LIST_FOREACH(spec, s, p->specs)
path_spec_mkdir(s, p->directory_mode);
}
static int path_start(Unit *u) {
Path *p = PATH(u);
int r;
assert(p);
assert(IN_SET(p->state, PATH_DEAD, PATH_FAILED));
r = unit_test_trigger_loaded(u);
if (r < 0)
return r;
r = unit_test_start_limit(u);
if (r < 0) {
path_enter_dead(p, PATH_FAILURE_START_LIMIT_HIT);
return r;
}
r = unit_acquire_invocation_id(u);
if (r < 0)
return r;
path_mkdir(p);
p->result = PATH_SUCCESS;
path_enter_waiting(p, true, false);
return 1;
}
static int path_stop(Unit *u) {
Path *p = PATH(u);
assert(p);
assert(IN_SET(p->state, PATH_WAITING, PATH_RUNNING));
path_enter_dead(p, PATH_SUCCESS);
return 1;
}
static int path_serialize(Unit *u, FILE *f, FDSet *fds) {
Path *p = PATH(u);
PathSpec *s;
assert(u);
assert(f);
assert(fds);
(void) serialize_item(f, "state", path_state_to_string(p->state));
(void) serialize_item(f, "result", path_result_to_string(p->result));
LIST_FOREACH(spec, s, p->specs) {
const char *type;
_cleanup_free_ char *escaped = NULL;
escaped = cescape(s->path);
if (!escaped)
return log_oom();
assert_se(type = path_type_to_string(s->type));
(void) serialize_item_format(f, "path-spec", "%s %i %s",
type,
s->previous_exists,
escaped);
}
return 0;
}
static int path_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
Path *p = PATH(u);
assert(u);
assert(key);
assert(value);
assert(fds);
if (streq(key, "state")) {
PathState state;
state = path_state_from_string(value);
if (state < 0)
log_unit_debug(u, "Failed to parse state value: %s", value);
else
p->deserialized_state = state;
} else if (streq(key, "result")) {
PathResult f;
f = path_result_from_string(value);
if (f < 0)
log_unit_debug(u, "Failed to parse result value: %s", value);
else if (f != PATH_SUCCESS)
p->result = f;
} else if (streq(key, "path-spec")) {
int previous_exists, skip = 0, r;
_cleanup_free_ char *type_str = NULL;
if (sscanf(value, "%ms %i %n", &type_str, &previous_exists, &skip) < 2)
log_unit_debug(u, "Failed to parse path-spec value: %s", value);
else {
_cleanup_free_ char *unescaped = NULL;
PathType type;
PathSpec *s;
type = path_type_from_string(type_str);
if (type < 0) {
log_unit_warning(u, "Unknown path type \"%s\", ignoring.", type_str);
return 0;
}
r = cunescape(value+skip, 0, &unescaped);
if (r < 0) {
log_unit_warning_errno(u, r, "Failed to unescape serialize path: %m");
return 0;
}
LIST_FOREACH(spec, s, p->specs)
if (s->type == type &&
path_equal(s->path, unescaped)) {
s->previous_exists = previous_exists;
break;
}
}
} else
log_unit_debug(u, "Unknown serialization key: %s", key);
return 0;
}
_pure_ static UnitActiveState path_active_state(Unit *u) {
assert(u);
return state_translation_table[PATH(u)->state];
}
_pure_ static const char *path_sub_state_to_string(Unit *u) {
assert(u);
return path_state_to_string(PATH(u)->state);
}
static int path_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
PathSpec *s = userdata;
Path *p;
int changed;
assert(s);
assert(s->unit);
assert(fd >= 0);
p = PATH(s->unit);
if (!IN_SET(p->state, PATH_WAITING, PATH_RUNNING))
return 0;
/* log_debug("inotify wakeup on %s.", UNIT(p)->id); */
LIST_FOREACH(spec, s, p->specs)
if (path_spec_owns_inotify_fd(s, fd))
break;
if (!s) {
log_error("Got event on unknown fd.");
goto fail;
}
changed = path_spec_fd_event(s, revents);
if (changed < 0)
goto fail;
if (changed)
path_enter_running(p);
else
path_enter_waiting(p, false, false);
return 0;
fail:
path_enter_dead(p, PATH_FAILURE_RESOURCES);
return 0;
}
static void path_trigger_notify(Unit *u, Unit *other) {
Path *p = PATH(u);
assert(u);
assert(other);
/* Invoked whenever the unit we trigger changes state or gains or loses a job */
/* Filter out invocations with bogus state */
assert(UNIT_IS_LOAD_COMPLETE(other->load_state));
/* Don't propagate state changes from the triggered unit if we are already down */
if (!IN_SET(p->state, PATH_WAITING, PATH_RUNNING))
return;
/* Propagate start limit hit state */
if (other->start_limit_hit) {
path_enter_dead(p, PATH_FAILURE_UNIT_START_LIMIT_HIT);
return;
}
/* Don't propagate anything if there's still a job queued */
if (other->job)
return;
if (p->state == PATH_RUNNING &&
UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
log_unit_debug(UNIT(p), "Got notified about unit deactivation.");
path_enter_waiting(p, false, true);
} else if (p->state == PATH_WAITING &&
!UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
log_unit_debug(UNIT(p), "Got notified about unit activation.");
path_enter_waiting(p, false, true);
}
}
static void path_reset_failed(Unit *u) {
Path *p = PATH(u);
assert(p);
if (p->state == PATH_FAILED)
path_set_state(p, PATH_DEAD);
p->result = PATH_SUCCESS;
}
static const char* const path_type_table[_PATH_TYPE_MAX] = {
[PATH_EXISTS] = "PathExists",
[PATH_EXISTS_GLOB] = "PathExistsGlob",
[PATH_DIRECTORY_NOT_EMPTY] = "DirectoryNotEmpty",
[PATH_CHANGED] = "PathChanged",
[PATH_MODIFIED] = "PathModified",
};
DEFINE_STRING_TABLE_LOOKUP(path_type, PathType);
static const char* const path_result_table[_PATH_RESULT_MAX] = {
[PATH_SUCCESS] = "success",
[PATH_FAILURE_RESOURCES] = "resources",
[PATH_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
[PATH_FAILURE_UNIT_START_LIMIT_HIT] = "unit-start-limit-hit",
};
DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);
const UnitVTable path_vtable = {
.object_size = sizeof(Path),
.sections =
"Unit\0"
"Path\0"
"Install\0",
.private_section = "Path",
.can_transient = true,
.can_fail = true,
.can_trigger = true,
.init = path_init,
.done = path_done,
.load = path_load,
.coldplug = path_coldplug,
.dump = path_dump,
.start = path_start,
.stop = path_stop,
.serialize = path_serialize,
.deserialize_item = path_deserialize_item,
.active_state = path_active_state,
.sub_state_to_string = path_sub_state_to_string,
.trigger_notify = path_trigger_notify,
.reset_failed = path_reset_failed,
.bus_set_property = bus_path_set_property,
};
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