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systemd/SOURCES/0565-Revert-udev-make-algor...

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From 897b4d1e19c706d9198b9308125df57a5d469a6b Mon Sep 17 00:00:00 2001
From: Michal Sekletar <msekleta@redhat.com>
Date: Mon, 17 May 2021 15:50:31 +0200
Subject: [PATCH] Revert "udev: make algorithm that selects highest priority
devlink less susceptible to race conditions"
This reverts commit 1d5f966c1758eb620755fcae54abd07a1ac36d3d.
Related: #1942299
---
src/udev/udev-event.c | 71 +++++-------
src/udev/udev-node.c | 244 ++++++++++++------------------------------
2 files changed, 99 insertions(+), 216 deletions(-)
diff --git a/src/udev/udev-event.c b/src/udev/udev-event.c
index 9004634f65..fd8406d959 100644
--- a/src/udev/udev-event.c
+++ b/src/udev/udev-event.c
@@ -833,41 +833,6 @@ static int rename_netif(struct udev_event *event) {
return 0;
}
-static void update_devnode(struct udev_event *event) {
- struct udev_device *dev = event->dev;
-
- if (major(udev_device_get_devnum(dev)) > 0) {
- bool apply;
-
- /* remove/update possible left-over symlinks from old database entry */
- if (event->dev_db != NULL)
- udev_node_update_old_links(dev, event->dev_db);
-
- if (!event->owner_set)
- event->uid = udev_device_get_devnode_uid(dev);
-
- if (!event->group_set)
- event->gid = udev_device_get_devnode_gid(dev);
-
- if (!event->mode_set) {
- if (udev_device_get_devnode_mode(dev) > 0) {
- /* kernel supplied value */
- event->mode = udev_device_get_devnode_mode(dev);
- } else if (event->gid > 0) {
- /* default 0660 if a group is assigned */
- event->mode = 0660;
- }
- else {
- /* default 0600 */
- event->mode = 0600;
- }
- }
-
- apply = streq(udev_device_get_action(dev), "add") || event->owner_set || event->group_set || event->mode_set;
- udev_node_add(dev, apply, event->mode, event->uid, event->gid, &event->seclabel_list);
- }
-}
-
void udev_event_execute_rules(struct udev_event *event,
usec_t timeout_usec, usec_t timeout_warn_usec,
struct udev_list *properties_list,
@@ -926,7 +891,35 @@ void udev_event_execute_rules(struct udev_event *event,
}
}
- update_devnode(event);
+ if (major(udev_device_get_devnum(dev)) > 0) {
+ bool apply;
+
+ /* remove/update possible left-over symlinks from old database entry */
+ if (event->dev_db != NULL)
+ udev_node_update_old_links(dev, event->dev_db);
+
+ if (!event->owner_set)
+ event->uid = udev_device_get_devnode_uid(dev);
+
+ if (!event->group_set)
+ event->gid = udev_device_get_devnode_gid(dev);
+
+ if (!event->mode_set) {
+ if (udev_device_get_devnode_mode(dev) > 0) {
+ /* kernel supplied value */
+ event->mode = udev_device_get_devnode_mode(dev);
+ } else if (event->gid > 0) {
+ /* default 0660 if a group is assigned */
+ event->mode = 0660;
+ } else {
+ /* default 0600 */
+ event->mode = 0600;
+ }
+ }
+
+ apply = streq(udev_device_get_action(dev), "add") || event->owner_set || event->group_set || event->mode_set;
+ udev_node_add(dev, apply, event->mode, event->uid, event->gid, &event->seclabel_list);
+ }
/* preserve old, or get new initialization timestamp */
udev_device_ensure_usec_initialized(event->dev, event->dev_db);
@@ -934,12 +927,6 @@ void udev_event_execute_rules(struct udev_event *event,
/* (re)write database file */
udev_device_tag_index(dev, event->dev_db, true);
udev_device_update_db(dev);
-
- /* Yes, we run update_devnode() twice, because in the first invocation, that is before update of udev database,
- * it could happen that two contenders are replacing each other's symlink. Hence we run it again to make sure
- * symlinks point to devices that claim them with the highest priority. */
- update_devnode(event);
-
udev_device_set_is_initialized(dev);
event->dev_db = udev_device_unref(event->dev_db);
diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c
index 2eeeccdd3a..333dcae6b9 100644
--- a/src/udev/udev-node.c
+++ b/src/udev/udev-node.c
@@ -13,27 +13,19 @@
#include <unistd.h>
#include "device-nodes.h"
-#include "device-private.h"
#include "dirent-util.h"
-#include "fd-util.h"
#include "format-util.h"
#include "fs-util.h"
-#include "sd-device.h"
#include "selinux-util.h"
#include "smack-util.h"
-#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "udev.h"
-#include "libudev-device-internal.h"
-#define LINK_UPDATE_MAX_RETRIES 128
-
-static int node_symlink(sd_device *dev, const char *node, const char *slink) {
+static int node_symlink(struct udev_device *dev, const char *node, const char *slink) {
struct stat stats;
char target[UTIL_PATH_SIZE];
char *s;
- const char *id_filename;
size_t l;
char slink_tmp[UTIL_PATH_SIZE + 32];
int i = 0;
@@ -97,10 +89,7 @@ static int node_symlink(sd_device *dev, const char *node, const char *slink) {
}
log_debug("atomically replace '%s'", slink);
- err = device_get_id_filename(dev, &id_filename);
- if (err < 0)
- return log_error_errno(err, "Failed to get id_filename: %m");
- strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", id_filename, NULL);
+ strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL);
unlink(slink_tmp);
do {
err = mkdir_parents_label(slink_tmp, 0755);
@@ -120,187 +109,104 @@ static int node_symlink(sd_device *dev, const char *node, const char *slink) {
if (err != 0) {
log_error_errno(errno, "rename '%s' '%s' failed: %m", slink_tmp, slink);
unlink(slink_tmp);
- } else
- /* Tell caller that we replaced already existing symlink. */
- return 1;
+ }
exit:
return err;
}
/* find device node of device with highest priority */
-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;
+static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize) {
+ struct udev *udev = udev_device_get_udev(dev);
+ DIR *dir;
struct dirent *dent;
- int r, priority = 0;
-
- assert(!add || dev);
- assert(stackdir);
- assert(ret);
+ int priority = 0;
+ const char *target = NULL;
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;
+ priority = udev_device_get_devlink_priority(dev);
+ strscpy(buf, bufsize, udev_device_get_devnode(dev));
+ target = buf;
}
dir = opendir(stackdir);
- if (!dir) {
- if (target) {
- *ret = TAKE_PTR(target);
- return 0;
- }
-
- return -errno;
- }
-
+ if (dir == NULL)
+ return target;
FOREACH_DIRENT_ALL(dent, dir, break) {
- _cleanup_(sd_device_unrefp) sd_device *dev_db = NULL;
- const char *devnode, *id_filename;
- int db_prio = 0;
+ struct udev_device *dev_db;
if (dent->d_name[0] == '\0')
break;
if (dent->d_name[0] == '.')
continue;
- log_debug("Found '%s' claiming '%s'", dent->d_name, stackdir);
-
- if (device_get_id_filename(dev, &id_filename) < 0)
- continue;
+ log_debug("found '%s' claiming '%s'", dent->d_name, stackdir);
/* did we find ourself? */
- if (streq(dent->d_name, id_filename))
- continue;
-
- if (sd_device_new_from_device_id(&dev_db, dent->d_name) < 0)
+ if (streq(dent->d_name, udev_device_get_id_filename(dev)))
continue;
- if (sd_device_get_devname(dev_db, &devnode) < 0)
- continue;
-
- if (device_get_devlink_priority(dev_db, &db_prio) < 0)
- continue;
-
- if (target && db_prio <= priority)
- continue;
-
- if (DEBUG_LOGGING) {
- const char *syspath = NULL;
-
- (void) sd_device_get_syspath(dev_db, &syspath);
- log_debug("Device '%s' claims priority %i for '%s'", strnull(syspath), db_prio, stackdir);
+ dev_db = udev_device_new_from_device_id(udev, dent->d_name);
+ if (dev_db != NULL) {
+ const char *devnode;
+
+ devnode = udev_device_get_devnode(dev_db);
+ if (devnode != NULL) {
+ if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
+ log_debug("'%s' claims priority %i for '%s'",
+ udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
+ priority = udev_device_get_devlink_priority(dev_db);
+ strscpy(buf, bufsize, devnode);
+ target = buf;
+ }
+ }
+ udev_device_unref(dev_db);
}
-
- r = free_and_strdup(&target, devnode);
- if (r < 0)
- return r;
- priority = db_prio;
}
-
- if (!target)
- return -ENOENT;
-
- *ret = TAKE_PTR(target);
- return 0;
+ closedir(dir);
+ return target;
}
-
/* manage "stack of names" with possibly specified device priorities */
-static int link_update(sd_device *dev, const char *slink, bool add) {
- _cleanup_free_ char *filename = NULL, *dirname = NULL;
- char name_enc[PATH_MAX];
- const char *id_filename;
- int i, r, retries;
-
- assert(dev);
- assert(slink);
-
- r = device_get_id_filename(dev, &id_filename);
- if (r < 0)
- return log_debug_errno(r, "Failed to get id_filename: %m");
+static void link_update(struct udev_device *dev, const char *slink, bool add) {
+ char name_enc[UTIL_PATH_SIZE];
+ char filename[UTIL_PATH_SIZE * 2];
+ char dirname[UTIL_PATH_SIZE];
+ const char *target;
+ char buf[UTIL_PATH_SIZE];
util_path_encode(slink + STRLEN("/dev"), name_enc, sizeof(name_enc));
- dirname = path_join(NULL, "/run/udev/links/", name_enc);
- if (!dirname)
- return log_oom();
- filename = path_join(NULL, dirname, id_filename);
- if (!filename)
- return log_oom();
-
- if (!add) {
- if (unlink(filename) == 0)
- (void) rmdir(dirname);
- } else
- for (;;) {
- _cleanup_close_ int fd = -1;
-
- r = mkdir_parents(filename, 0755);
- if (!IN_SET(r, 0, -ENOENT))
- return r;
-
- fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
- if (fd >= 0)
- break;
- if (errno != ENOENT)
- return -errno;
- }
-
- /* If the database entry is not written yet we will just do one iteration and possibly wrong symlink
- * will be fixed in the second invocation. */
- (void) sd_device_get_is_initialized(dev, &r);
- retries = r > 0 ? LINK_UPDATE_MAX_RETRIES : 1;
+ strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
+ strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
- for (i = 0; i < retries; i++) {
- _cleanup_free_ char *target = NULL;
- struct stat st1 = {}, st2 = {};
+ if (!add && unlink(filename) == 0)
+ rmdir(dirname);
- r = stat(dirname, &st1);
- if (r < 0 && errno != ENOENT)
- return -errno;
-
- r = link_find_prioritized(dev, add, dirname, &target);
- if (r == -ENOENT) {
- log_debug("No reference left, removing '%s'", slink);
- if (unlink(slink) == 0)
- (void) rmdir_parents(slink, "/");
-
- break;
- } else if (r < 0)
- return log_error_errno(r, "Failed to determine highest priority symlink: %m");
+ target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
+ if (target == NULL) {
+ log_debug("no reference left, remove '%s'", slink);
+ if (unlink(slink) == 0)
+ rmdir_parents(slink, "/");
+ } else {
+ log_debug("creating link '%s' to '%s'", slink, target);
+ node_symlink(dev, target, slink);
+ }
- r = node_symlink(dev, target, slink);
- if (r < 0) {
- (void) unlink(filename);
- break;
- } else if (r == 1)
- /* We have replaced already existing symlink, possibly there is some other device trying
- * to claim the same symlink. Let's do one more iteration to give us a chance to fix
- * the error if other device actually claims the symlink with higher priority. */
- continue;
+ if (add) {
+ int err;
- /* Skip the second stat() if the first failed, stat_inode_unmodified() would return false regardless. */
- if ((st1.st_mode & S_IFMT) != 0) {
- r = stat(dirname, &st2);
- if (r < 0 && errno != ENOENT)
- return -errno;
+ do {
+ int fd;
- if (stat_inode_unmodified(&st1, &st2))
+ err = mkdir_parents(filename, 0755);
+ if (!IN_SET(err, 0, -ENOENT))
break;
- }
+ fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
+ if (fd >= 0)
+ close(fd);
+ else
+ err = -errno;
+ } while (err == -ENOENT);
}
-
- return i < LINK_UPDATE_MAX_RETRIES ? 0 : -ELOOP;
}
void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old) {
@@ -327,7 +233,7 @@ void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev
log_debug("update old name, '%s' no longer belonging to '%s'",
name, udev_device_get_devpath(dev));
- link_update(dev->device, name, false);
+ link_update(dev, name, false);
}
}
@@ -432,16 +338,11 @@ void udev_node_add(struct udev_device *dev, bool apply,
xsprintf_dev_num_path(filename,
streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
udev_device_get_devnum(dev));
- node_symlink(dev->device, udev_device_get_devnode(dev), filename);
+ node_symlink(dev, udev_device_get_devnode(dev), filename);
/* create/update symlinks, add symlinks to name index */
- udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev)) {
- int r;
-
- r = link_update(dev->device, udev_list_entry_get_name(list_entry), true);
- if (r < 0)
- log_info_errno(r, "Failed to update device symlinks: %m");
- }
+ udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
+ link_update(dev, udev_list_entry_get_name(list_entry), true);
}
void udev_node_remove(struct udev_device *dev) {
@@ -449,13 +350,8 @@ void udev_node_remove(struct udev_device *dev) {
char filename[DEV_NUM_PATH_MAX];
/* remove/update symlinks, remove symlinks from name index */
- udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev)) {
- int r;
-
- r = link_update(dev->device, udev_list_entry_get_name(list_entry), false);
- if (r < 0)
- log_info_errno(r, "Failed to update device symlinks: %m");
- }
+ udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
+ link_update(dev, udev_list_entry_get_name(list_entry), false);
/* remove /dev/{block,char}/$major:$minor */
xsprintf_dev_num_path(filename,
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