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udev: export tags of "dead" device nodes to /run/udev/static_node-tags/

Browse source 
Based on a patch by Kay Sievers.

A tag is exported at boot as a symlinks to the device node in the folder
/run/udev/static_node-tags/<tagname>/, if the device node exists.

These tags are cleaned up by udevadm info --cleanup-db, but are otherwise
never removed.
This commit is contained in:
Tom Gundersen 2013-07-07 18:32:34 +02:00
parent 6cf2f1d94d
commit 84b6ad702e
6 changed files with 88 additions and 19 deletions
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10
man/udev.xml
View file

@ -521,9 +521,13 @@
<term><option>static_node=</option></term>
<listitem>
<para>Apply the permissions specified in this rule to the static device node with
the specified name. Static device node creation can be requested by kernel modules.
These nodes might not have a corresponding kernel device at the time systemd-udevd is
started; they can trigger automatic kernel module loading.</para>
the specified name. Also, for every tag specified in this rule, create a symlink
in the directory
<filename>/run/udev/static_node-tags/<replaceable>tag</replaceable></filename>
pointing at the static device node with the specified name. Static device node
creation is performed by systemd-tmpfiles before systemd-udevd is started. The
static nodes might not have a corresponding kernel device; they are used to
trigger automatic kernel module loading when they are accessed.</para>
</listitem>
</varlistentry>
<varlistentry>

3
src/login/70-uaccess.rules
View file

@ -25,7 +25,8 @@ SUBSYSTEM=="block", ENV{ID_CDROM}=="1", TAG+="uaccess"
SUBSYSTEM=="scsi_generic", SUBSYSTEMS=="scsi", ATTRS{type}=="4|5", TAG+="uaccess"
# Sound devices
SUBSYSTEM=="sound", TAG+="uaccess"
SUBSYSTEM=="sound", TAG+="uaccess" \
OPTIONS+="static_node=snd/timer", OPTIONS+="static_node=snd/seq"
# ffado is an userspace driver for firewire sound cards
SUBSYSTEM=="firewire", ENV{ID_FFADO}=="1", TAG+="uaccess"

82
src/udev/udev-rules.c
View file

@ -33,6 +33,7 @@
#include "path-util.h"
#include "conf-files.h"
#include "strbuf.h"
#include "strv.h"
#define PREALLOC_TOKEN 2048
@ -152,9 +153,9 @@ enum token_type {
TK_A_OWNER_ID, /* uid_t */
TK_A_GROUP_ID, /* gid_t */
TK_A_MODE_ID, /* mode_t */
TK_A_TAG, /* val */
TK_A_STATIC_NODE, /* val */
TK_A_ENV, /* val, attr */
TK_A_TAG, /* val */
TK_A_NAME, /* val */
TK_A_DEVLINK, /* val */
TK_A_ATTR, /* val, attr */
@ -2496,16 +2497,21 @@ int udev_rules_apply_to_event(struct udev_rules *rules, struct udev_event *event
}
}
void udev_rules_apply_static_dev_perms(struct udev_rules *rules)
int udev_rules_apply_static_dev_perms(struct udev_rules *rules)
{
struct token *cur;
struct token *rule;
uid_t uid = 0;
gid_t gid = 0;
mode_t mode = 0;
_cleanup_strv_free_ char **tags = NULL;
char **t;
FILE *f = NULL;
_cleanup_free_ char *path = NULL;
int r = 0;
if (rules->tokens == NULL)
return;
return 0;
cur = &rules->tokens[0];
rule = cur;
@ -2522,6 +2528,8 @@ void udev_rules_apply_static_dev_perms(struct udev_rules *rules)
uid = 0;
gid = 0;
mode = 0;
strv_free(tags);
tags = NULL;
break;
case TK_A_OWNER_ID:
uid = cur->key.uid;
@ -2531,19 +2539,53 @@ void udev_rules_apply_static_dev_perms(struct udev_rules *rules)
break;
case TK_A_MODE_ID:
mode = cur->key.mode;
break;
case TK_A_TAG:
r = strv_extend(&tags, rules_str(rules, cur->key.value_off));
if (r < 0)
goto finish;
break;
case TK_A_STATIC_NODE: {
char filename[UTIL_PATH_SIZE];
char device_node[UTIL_PATH_SIZE];
char tags_dir[UTIL_PATH_SIZE];
char tag_symlink[UTIL_PATH_SIZE];
struct stat stats;
/* we assure, that the permissions tokens are sorted before the static token */
if (mode == 0 && uid == 0 && gid == 0)
if (mode == 0 && uid == 0 && gid == 0 && tags == NULL)
goto next;
strscpyl(filename, sizeof(filename), "/dev/", rules_str(rules, cur->key.value_off), NULL);
if (stat(filename, &stats) != 0)
strscpyl(device_node, sizeof(device_node), "/dev/", rules_str(rules, cur->key.value_off), NULL);
if (stat(device_node, &stats) != 0)
goto next;
if (!S_ISBLK(stats.st_mode) && !S_ISCHR(stats.st_mode))
goto next;
if (tags) {
/* Export the tags to a directory as symlinks, allowing otherwise dead nodes to be tagged */
STRV_FOREACH(t, tags) {
_cleanup_free_ char *unescaped_filename = NULL;
strscpyl(tags_dir, sizeof(tags_dir), "/run/udev/static_node-tags/", *t, "/", NULL);
r = mkdir_p(tags_dir, 0755);
if (r < 0) {
log_error("failed to create %s: %s\n", tags_dir, strerror(-r));
return r;
}
unescaped_filename = xescape(rules_str(rules, cur->key.value_off), "/.");
strscpyl(tag_symlink, sizeof(tag_symlink), tags_dir, unescaped_filename, NULL);
r = symlink(device_node, tag_symlink);
if (r < 0 && errno != EEXIST) {
log_error("failed to create symlink %s -> %s: %s\n", tag_symlink, device_node, strerror(errno));
return -errno;
} else
r = 0;
}
}
if (mode == 0) {
if (gid > 0)
mode = 0660;
@ -2551,20 +2593,20 @@ void udev_rules_apply_static_dev_perms(struct udev_rules *rules)
mode = 0600;
}
if (mode != (stats.st_mode & 01777)) {
chmod(filename, mode);
log_debug("chmod '%s' %#o\n", filename, mode);
chmod(device_node, mode);
log_debug("chmod '%s' %#o\n", device_node, mode);
}
if ((uid != 0 && uid != stats.st_uid) || (gid != 0 && gid != stats.st_gid)) {
chown(filename, uid, gid);
log_debug("chown '%s' %u %u\n", filename, uid, gid);
chown(device_node, uid, gid);
log_debug("chown '%s' %u %u\n", device_node, uid, gid);
}
utimensat(AT_FDCWD, filename, NULL, 0);
utimensat(AT_FDCWD, device_node, NULL, 0);
break;
}
case TK_END:
return;
goto finish;
}
cur++;
@ -2574,4 +2616,18 @@ next:
cur = rule + rule->rule.token_count;
continue;
}
finish:
if (f) {
fflush(f);
fchmod(fileno(f), 0644);
if (ferror(f) || rename(path, "/run/udev/static_node-tags") < 0) {
r = -errno;
unlink("/run/udev/static_node-tags");
unlink(path);
}
fclose(f);
}
return r;
}

2
src/udev/udev.h
View file

@ -72,7 +72,7 @@ struct udev_rules *udev_rules_new(struct udev *udev, int resolve_names);
struct udev_rules *udev_rules_unref(struct udev_rules *rules);
bool udev_rules_check_timestamp(struct udev_rules *rules);
int udev_rules_apply_to_event(struct udev_rules *rules, struct udev_event *event, const sigset_t *sigmask);
void udev_rules_apply_static_dev_perms(struct udev_rules *rules);
int udev_rules_apply_static_dev_perms(struct udev_rules *rules);
/* udev-event.c */
struct udev_event *udev_event_new(struct udev_device *dev);

6
src/udev/udevadm-info.c
View file

@ -251,6 +251,12 @@ static void cleanup_db(struct udev *udev)
closedir(dir);
}
dir = opendir("/run/udev/static_node-tags");
if (dir != NULL) {
cleanup_dir(dir, 0, 2);
closedir(dir);
}
dir = opendir("/run/udev/watch");
if (dir != NULL) {
cleanup_dir(dir, 0, 1);

4
src/udev/udevd.c
View file

@ -1197,7 +1197,9 @@ int main(int argc, char *argv[])
}
log_debug("set children_max to %u\n", children_max);
udev_rules_apply_static_dev_perms(rules);
rc = udev_rules_apply_static_dev_perms(rules);
if (rc < 0)
log_error("failed to apply permissions on static device nodes - %s\n", strerror(-rc));
udev_list_node_init(&event_list);
udev_list_node_init(&worker_list);